p53 plays an important role to advance genomic candor from cellular accent by trans-activating the after genes complex in altered cellular functions, such as corpuscle aeon arrest (Slingerland and Benchimol, 1991; el-Deiry et al., 1993; Tanaka et al., 2000) and apoptosis (Miyashita and Reed, 1995; Owen-Schaub et al., 1995; Polyak et al., 1997; Oda et al., 2000). Cellular stress, including DNA accident and hypoxia, stabilizes p53 protein by post-transcriptional modification, such as phosphorylation (Sakaguchi et al., 1998; Ashcroft et al., 1999), acetylation (Barlev et al., 2001) and prolyl isomerization (Zacchi et al., 2002; Zheng et al., 2002) in specific residues alfresco the axial DNA-binding domain, converting the abeyant anatomy of p53 into the alive form. p53 acts as a tetramer through the carboxy-terminal oligomerization area and several studies accept apparent the accent of this area for p53 transcriptional activity, bump suppressive action and ascendant abrogating aftereffect of p53 (Shaulian et al., 1992, 1993; Unger et al., 1992; Halazonetis and Kandil, 1993). The anatomy of the oligomerization area has been apparent by both X-ray crystallography and NMR (Lee et al., 1994; Clore et al., 1995; Jeffrey et al., 1995; Miller et al., 1996; Chene et al., 1997; Mittl et al., 1998) and the structural advice of specific residues in the apparent ‘V-shaped’ structures is advantageous to bigger accept oligomerization. However, the addition of anniversary balance in oligomerization has not been accurate biochemically.
Previously, we accept about mutagenized the area by an error-prone PCR address and yeast-based anatomic appraisal (Ishioka et al., 1995). We accept abandoned two absorbing aberrant p53s encoded by two missense mutations. The aboriginal mutant, L344P, articular as a accident of transactivation mutant, is amid in the α-helix and had no adeptness to anatomy dimers or tetramers (monomer mutant). The additional mutant, K351E, articular as a partial-transactivation mutant, has the adeptness to anatomy dimers but not tetramers (dimer mutant) (Ishioka et al., 1997). L344P is not alone abnormal in the in vitro beginning ambience but additionally in the pathogenic ambience because it has been appear as a adroit germline alteration in a ancestors with archetypal Li–Fraumeni affection (Varley et al., 1996). This aberrant p53 is additionally apparent to be a monomer aberrant (Ishioka et al., 1997; Davison et al., 1998; Lomax et al., 1998). These after-effects advance that oligomer (either dimer or tetramer) accumulation is capital for the p53 transactivation action and appearance that mutations abnormal in oligomer accumulation are as pathogenic as accepted mutations in the DNA-binding domain. Although the accent of several specific residues for both oligomer accumulation and transcriptional action accept been approved by an alanine barter at nine residues in the area (Chene et al., 1997; Mateu and Fersht, 1998; Chene and Bechter, 1999), added advice about the relationships amid p53 structure, transactivation action and oligomer accumulation is all-important to annotate the bump suppressive role of p53 oligomer formation. Recently, we accept complete all accessible amino-acid substitutions acquired by point mutations throughout the protein (5.9 barter per residue) and accept apparent that aberrant p53s in the oligomerization area are acute in transcriptional activities in aggrandize and antiseptic interrelations amid their transcriptional activities and the anatomy (Kato et al., 2003).
To investigate whether the oligomer accumulation correlates with the transactivation action and the structural advice of the oligomerization domain, we ysed the adeptness to anatomy oligomers and compared the after-effects with the accepted advice on the transactivation and the structure. Amid 193 aberrant p53s complete in 33 residues from 322 to 354, we chose to appraise 184 (95.3%) aberrant p53s. The aberrant p53s or wild-type p53 protein bidding in aggrandize beef were incubated in the attendance or absence of 0.1% glutaraldehyde (a cross-linker) and were afar by SDS/PAGE with a 5–15% polyacrylamide gradient. The p53 protein was visualized by immunoblotting appraisal application a polyclonal p53 antibody. The after-effects of adumbrative residue, in which aberrant p53s predominantly anatomy tetramer (R336) or dimer (E343), or either tetramer, dimer, or monomer depending on the amino-acid barter (A347), are apparent in Figure 1. The after-effects of all 184 aberrant p53s are abbreviated in Figure 2. In wild-type p53, alone the tetramer anatomy was empiric and no or a trace monomer and dimer anatomy was arresting in the attendance of glutaraldehyde, advertence that wild-type p53 predominantly forms tetramers (Figure 1). In contrast, neither dimers nor tetramers were formed in the accepted monomer aberrant L344P as appear ahead (Ishioka et al., 1997) (Figure 1).
Analysis of oligomer accumulation of aberrant p53s. The p53-expressing aggrandize beef were able in 1.2 ml of complete complete (SC) aqueous media at 30°C for 16 h in a 96-well plates and 0.4 ml of the adeptness average was inoculated in 0.8 ml of aggrandize extract/peptone/dextrose (YPD) aqueous media and added able at 37°C for 6 h. The beef were precipitated by centrifugation and resuspended in 200 μl of DOC absorber (Ishioka et al., 1997). The beef were again genized application a Mixer Mill MM300 (Qiagen) with bottle chaplet for 1 min and algid for 1 min on ice four times. In total, 25 μl of corpuscle lysates were incubated at allowance temperature for 20 min in the absence or attendance of 0.1% glutaraldehyde (a cross-linking agent) and aloft in a sample loading absorber absolute 1% SDS. The acknowledgment mixtures were afar by SDS/PAGE (with a 5–15% polyacrylamide gradient), followed by immunoblotting appraisal application a HRP-conjugated polyclonal p53 antibiotic (FL-393, Santa Cruz). The p53 protein was visualized application an added chemiluminescent address (ECL kit, Amersham). (a) Aberrant p53s in Glu336 predominantly anatomy tetramers as wild-type p53 (WT). One (R335L) of added tetramer mutants was additionally shown. (b) Aberrant p53s in Glu343 predominantly anatomy dimers. WT and L344P are tetramer and monomer controls, respectively. (c) Aberrant p53s in Ala347 anatomy monomers (A347P), dimers (A347T, A347S, A347D and A347V) and tetramers (A347G) depending on the specific aberrant p53. GA is adumbrated in the absence (−) or attendance ( ) of 0.1% glutaraldehyde. We agenda that monomeric p53 forms of L344P and L347P assume to be ambiguous in our beginning ambience because of alien reason
The adeptness to anatomy oligomers and transactivate p53 ambition genes on 184 aberrant p53s. The adeptness to anatomy oligomers of anniversary aberrant p53 is adumbrated graphically from the NH2 terminal allocation (top panel) to the COOH terminal allocation (bottom panel). A absolute of 10 aberrant p53s were not advised and are adumbrated as dejected bars. The adeptness to transactivate eight p53 ambition genes on anniversary aberrant p53 originated from our antecedent abstraction (Kato et al., 2003) and showed a blush arrangement according to the affiliated bulk of transactivity (reference bar). Red, blooming or atramentous indicates higher, lower or average activity, respectively). Aberrant p53s appear as actual alteration (p53 web site, http://p53.free.fr/) were apparent (closed circle) by the cardinal of alteration frequencies
The oligomerization area consists of two accessory structures, a β-strand (residues 326–333) and an α-helix (residues 335–354), and the two structures anatomy a V-shaped anatomy affiliated by a articulation balance at G334 (Clore et al., 1995). Of the 33 residues ysed, 24 residues were afflicted with the oligomer accumulation by at atomic one aberrant p53. All four residues (P322, L323, D324 and G325) alfresco of the accessory structures and bristles (E326, Y327, F328, T329 and Q331) of eight residues in the β-strand were not acute to amino-acid substitutions. Like wild-type p53, all aberrant p53s in nine residues predominantly formed tetramers (tetramer mutant), although a baby bulk of the dimer anatomy was additionally apparent in some aberrant p53s of these residues (data not shown). Figure 1a indicates adumbrative tetramer aberrant p53s in the E336 residue. In contrast, all but four (R335, E336, E339 and Q354) residues in the α-helix (16 of 20) as able-bodied as the articulation balance (G334) were acute for amino-acid substitutions.
A baby berserk array consisting of the ancillary chains of three amino acids, I332, F338 and F341, causes a V-shaped anatomy (Clore et al., 1995). Amid the aberrant p53s in three residues, bristles of six mutants in F341 were clumsy to anatomy tetramers. There were four monomer mutants (F341V, F341Y, F341S and F341C) and one dimer (F341L) mutant. In balance I332, two (I332N and I332S) of the six mutants were monomer mutants and the actual four mutants represented absolute tetramer formation. In contrast, the six mutants in F338 did not affect the tetramer formation.
Two p53 monomers accessory via their β-strands to anatomy an antiparallel double-stranded area and via the antiparallel affiliation of their α-helix to actualize a double-helical array (Clore et al., 1995). Eight residues, F328, L330, I332, R337, F338, F341, N345 and D352, are complex in the monomer–monomer interaction. A berserk amount assembles berserk residues including F328, L330 and I332 from the β-strands and F338, F341 and N345 from the α-helix (Clore et al., 1995). All residues but two (F328 and F338, see above) were acute to amino-acid substitutions and, as expected, abounding of the aberrant p53s (17 of 48) complete in these residues were monomer mutants. These were three mutants (L330H, L330P and L330R) in L330, two mutants (I332N and I332S) in I332, all advised mutants (R337S, R337G, R337C, R337P and R337L) in R337, four mutants (F341V, F341Y, F341S and F341C) in F341 and three mutants (N345H, N345Y and N345T) in N345. Two specific residues, R337 from one monomer and D352 from the added monomer, accomplish a alkali arch (Clore et al., 1995); however, interestingly, the biochemical furnishings of mutants in the two residues were different. Admitting all advised mutants in R337 were monomer mutants, all six mutants (D352N, D352H, D352Y, D352A, D352G and D352V) complete on D352 were dimer mutants, advertence that D352 may be a added important balance for dimmer–dimer alternation rather than for monomer–monomer interaction. Three added dimer mutants (F341L, N345D, N345S) were additionally begin in this category, suggesting the accent of F341 and N345 in dimmer–dimer alternation (see below).
Two dimers accessory through bifold circling bundles, and the dimmer–dimer alternation involves berserk residues in the α-helix, M340, F341, L344, A347, L348 and L350 (Clore et al., 1995). As expected, abounding of the aberrant p53s (11 of 33) complete in these residues were dimer mutants. There were two mutants (M340K and M340R) in M340, one aberrant (F341L) in F341, one aberrant (L344M) in L344, four mutants (A347 T, A347S, A347D and A347V) in A347 (Figure 1c), two mutants (L348W and L348F) in L348 and one aberrant (L350R) in L350. Interestingly, best of the aberrant p53s in F341 (four of six, F341V, F341Y, F341S and F341C) and L344 (three of four, L344Q, L344P and L344R) were monomer mutants, and the actual mutants independent dimer mutants (F341L and L344M). These after-effects adumbrated that, agnate to F341, L344 and N345 (see above) are additionally important for both monomer–monomer alternation and dimmer–dimer interaction.
Eight residues (R333, R342, E343, E346, E349, K351, A353 and Q354) accept not been defined in the antecedent structural studies. Amid the mutants in these residues, six (R333P, R342P, E349K and E349V) were monomer mutants, advertence that R333, R342 and E349 may accord to monomer–monomer interaction. There were 13 dimer mutants. All mutants (E343K, E343Q, E343A, E343G, E343V and E343D) in E343 (Figure 1b) and all (E346K, E346Q, E346A, E346G and E346V) but one aberrant in E346 were dimer mutants, advertence that these two residues are important for dimmer–dimer interaction. There were two added dimer mutants, including K351E, a accepted dimer aberrant (Ishioka et al., 1997), and A353P, suggesting that these two residues are additionally complex in dimmer–dimer interaction. Neither monomer nor dimer mutants were begin in Q354.
The monomer mutants tended to array in the residues complex in the monomer–monomer interface (Supplementary Figure 1) and the dimer mutants tended to array in the residues complex in the dimmer–dimer interface (Supplementary Figure 2). These after-effects announce that the adeptness to anatomy oligomers of p53 mutants in the tetramerization area and the anatomy are able-bodied interrelated. The adeptness to anatomy oligomers of p53 mutants in the tetramerization area and their adeptness to transactivate after genes are abbreviated in Table 1. Obviously, the α-helix was added acute to amino-acid substitutions than the β-strand and the bend in the 33 amino-acid peptides, alike if the β-strand was conserved as able-bodied as the α-helix (Figure 3). All dimer mutants and the majority of monomer mutants are begin in the α-helix. There was character in the affiliation amid oligomer accumulation and transcriptional activity, that is, monomer mutants were transcriptionally abeyant admitting dimer and tetramer mutants retained their transcriptional activity. These abstracts additionally advance that alone TP53 mutations encoding monomer mutants may be pathogenic, admitting those of dimer mutants may not. Amid the 193 aberrant p53s complete in the fragment, alone 78 aberrant p53s accept been appear as actual missense mutations in the TP53 alteration databases. Surprisingly, bisected of these TP53 missense mutations did not encode biochemically and/or transcriptionally abeyant aberrant p53s. Amid the appear mutants, all but three abeyant mutants (Q331P, R337C and R337H) accept been appear alone three times or less. According to our appraisal of the TP53 alteration database, the TP53 mutations appear beneath than three times are apprehensive (accidental mutations or abstruse errors) for their anatomic aftereffect on carcinogenesis (Soussi et al., 2005, and abstruse data). Real pathogenic mutations, therefore, assume to be actual few although 23.9% (44 of 184) encoded transcriptionally abeyant aberrant p53s such as accepted aberrant p53s that occurred in the DNA-binding area (Table 1). While the oligomer accumulation was carefully affiliated to the p53 transactivation function, the inactivation of oligomerization seems bereft to abate the abounding p53 bump suppressive function. We adduce two accessible explanations: first, such aberrant p53s abnormal in oligomerization accept no trans-dominant aftereffect as appear in some aberrant p53s in the DNA-binding area (Srivastava et al., 1993, Brachmann et al., 1996) because the aftereffect requires p53 oligomer accumulation (Shaulian et al., 1993, Unger et al., 1993); second, transactivation is not the alone action of p53-mediated bump aishment apoptosis. There are abounding letters acknowledging the accent of the transactivation-independent cytoplasmic action of p53 (Marchenko et al., 2000; Mihara et al., 2003; Kakudo et al., 2005) and aberrant p53s abnormal in oligomerization adeptness absorb the function. We agenda that these possibilities may explain, at atomic in part, why beneath mutations accept been appear in the carboxyl terminal domain.
3D-structure and anatomic backdrop of p53 tetramerization domain. The 3D-structure p53 tetramerization area was based on 3SAK (PDB) and was apparent as award diagram (left panel) for courage anatomy or brawl diagram (right panel) absolute the ancillary alternation structure. (a) Residues from 322 to 354 were evaluated based on the transcriptional action of anniversary aberrant p53 (Kato et al., 2003) and colored. Red, transactivity of any aberrant p53s in a balance was not affected. Green, a balance in which transactivity of at atomic one aberrant p53 was inactivated. (b) Residues from 322 to 354 were black based on the oligomerization adeptness of aberrant p53s. Red, a balance in which any aberrant p53s were tetramer mutants. Light blue, a balance in which at atomic one aberrant p53 was monomer mutant. Yellow, a balance in which at atomic one aberrant p53 was dimer aberrant and no aberrant p53 was monomer mutant. Gray in both (a) and (b), unexamined residues in the 3SAK
Among the 184 aberrant p53s, there were 22 exceptions to the oligomerization–transactivation relationship, including four monomer mutants (N345H, N345Y, N345K, E349K) that retained transcriptional activity, 12 tetramer mutants (F328V, F328S, I332F, I332T, I332M, R333G, G334W, G334A, F338I, F338V, F338S, F338C) and six dimer mutants (N345D, A347T, A347D, A347V, L348W, K351E) that were transcriptionally inactive. We agenda that bisected of them (F328V, I332F, I332M, R333G, G334A, F338I, F338V, F338C, A347T, A347V, L348W) retained fractional transactivity. Although the atomic apparatus of the alterity in anniversary aberrant p53 is still unclear, we brainstorm at atomic two possibilities answer the exceptions. First, our two beginning systems (both transactivation appraisal and oligomer accumulation ysis) may not consistently represent a attenuate ecology aberration and that the oligomerization cachet in the active beef adeptness alter from that in aggrandize corpuscle lysates depending on ecology factors such as pH. Second, some of the exceptions may affect the cellular localization of p53 rather than the oligomer formation. The p53 nuclear localization is adapted by its nuclear acceptation and nuclear consign in beastly cells. Especially, the nuclear consign is adapted by MDM2 bounden to the NH2 terminal transactivation area of p53 (Roth et al., 1998; Tao et al., 1999) and by CRM1 bounden to a nuclear consign arresting (NES) in the α-helix allocation of the tetramerization area (residues 340–351) (Stommel et al., 1999). Therefore, not alone oligomer accumulation but additionally nuclear consign of p53 may affect the transactivation although there has never been a abstraction assuming the cellular localization of the p53 protein in yeast.
Apart from the exceptions, there were at atomic two cases with alterity amid the accepted abstraction and the antecedent report. One aberrant p53, R337H, showed a altered aftereffect from the antecedent report. R337H has been appear in Brazilian adolescence adrenocortical carcinoma, is awful acute to pH on its tetramerization and retains wild-type action beneath the physiological pH action (DiGiammarino et al., 2002). In contrast, R337H was a monomer aberrant beneath our cross-linking altitude and was mostly abeyant in archetype appraisal in our beginning arrangement (Figure 2). We brainstorm that there adeptness be slight differences in pH, redox ascendancy and thiol agreeable amid animal and aggrandize beef and this adeptness be a acumen answer the discrepancy. Another aberrant p53 is D352A, which has been appear as a tetramer aberrant back it is bidding as a baby p53 peptide (Mateu and Fersht, 1998) but was a dimer aberrant in feature p53 in this study. We brainstorm that the alfresco of the oligomerization area adeptness affect the oligomer formation.
In the tetramerization domain, 12 residues (D324, E326, L330, I332, R333, G334, F338, E339, M340, E346, L348 and L350) are able-bodied conserved amid bearcat p53 and p53 ancestors associates (Supplementary Figure 3). However, their acuteness to mutations in oligomer accumulation and their transcriptional action were different. In all, 10 monomer and 10 dimer mutants were empiric in this category, but no oligomer abnormal or transcriptionally abeyant aberrant was begin in the four (D324, E326, F338 and E339) residues. Therefore, it seems difficult to adumbrate the anatomic appulse of mutations from specific amino-acid barter and amino-acid attention in the domain.
In conclusion, we assiduously ysed the p53 oligomerization area by application a absolute p53 missense alteration library and showed the accord amid oligomer formation, transactivation and the structure. We showed the aboriginal affirmation that p53 oligomerization is carefully accompanying to sequence-specific transactivation in anniversary aberrant p53 level. The abstracts presented actuality accentuate the antecedent abstracts assuming the accent of the p53 oligomerization area for the sequence-specific transactivation and should be advantageous to bigger accept the anatomy and action accord of p53 and possibly added oligomer proteins.
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