1. ¹Institute of Genetics and Cytology, Northeast Normal University, Changchun, China
2. ²Key Laboratory for Applied Statistics of MOS, Northeast Normal University, Changchun, China

Correspondence: Dr J Lu, Institute of Genetics and Cytology, Northeast Normal University, 5268 Renmin Street, Changchun 130024, China. E-mails: luj809@nenu.edu.cn, ycsuo@nenu.edu.cn

³These authors contributed equally to this work.

Received 27 March 2007; Revised 22 August 2007; Accepted 22 August 2007; Published online 1 October 2007.

Abstract

As a cyclin-dependent kinase inhibitor, p16^INK4a plays a key role in cell cycle progression and cellular differentiation, and its expression is frequently altered in human cancers through epigenetically mediated transcriptional silencing. In this report, we demonstrate that p300 was able to induce cell cycle arrest, and this process was reversed by p16^INK4a silencing by RNA interference in HeLa cells. We also show that p300 was involved in activation of p16^INK4a expression in 293T cells. Specifically, p300 cooperated with Sp1 to stimulate both p16^INK4a promoter activity and mRNA expression. Co-immunoprecipitation and mammalian two-hybrid assays revealed that p300 and Sp1 formed a complex through interaction between the Q domain of p300 and the N-terminal domain of Sp1. The chromatin immunoprecipitation assays verified that p300 was recruited to p16^INK4a promoter, and the histone acetyltransferase domain of p300 participated in p16^INK4a activation through inducing hyperacetylation of histone H4 at p16^INK4a gene. These data suggest that p300 plays a critical role in transcriptional regulation of p16^INK4a and in cell cycle arrest.