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Open Access item The C/H3 Domain of p300 is required to protect VRK1 and VRK2 from their downregulation induced by p53
Vega, Francisco M.
Lazo, Pedro A.
|Keywords:||VRK1, VRK2, Ran, kinase, Regulation, interaction|
|Series/Report no.:||PLoS ONE|
3: e2649 (2008)
|Abstract:||Background: The vaccinia-related kinase 1 (VRK1) protein, an activator of p53, can be proteolytically downregulated by an
indirect mechanism, which requires p53-dependent transcription.
Principal Findings: In this work we have biochemically characterized the contribution of several p53 transcriptional
cofactors with acetyl transferase activity to the induction of VRK1 downregulation that was used as a functional assay.
Downregulation of VRK1 induced by p53 is prevented in a dose dependent manner by either p300 or CBP, but not by PCAF,
used as transcriptional co-activators, suggesting that p53 has a different specificity depending on the relative level of these
transcriptional cofactors. This inhibition does not require p53 acetylation, since a p53 acetylation mutant also induces VRK1
downregulation. PCAF can not revert the VRK1 protection effect of p300, indicating that these two proteins do not compete
for a common factor needed to induce VRK1 downregulation. The protective effect is also induced by the C/H3 domain of
p300, a region implicated in binding to several transcription factors and SV40 large T antigen; but the protective effect is
lost when a mutant C/H3Del33 is used. The protective effect is a consequence of direct binding of the C/H3 domain to the
transactivation domain of p53. A similar downregulatory effect can also be detected with VRK2 protein.
Conclusions/Significance: Specific p53-dependent effects are determined by the availability and ratios of its transcriptional
cofactors. Specifically, the downregulation of VRK1/VRK2 protein levels, as a consequence of p53 accumulation, is thus
dependent on the levels of the p300/CBP protein available for transcriptional complexes, since in this context this cofactor
functions as a repressor of the effect. These observations point to the relevance of knowing the cofactor levels in order to
determine one effect or another.|
|Appears in Collections:||(IBMCC) Artículos|
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