The p53 Tumor Suppressor Protein Represses Human snRNA Gene Transcription by RNA Polymerases II and III Independently of Sequence-Specific DNA Binding

Abstract

Human U1 and U6 snRNA genes are transcribed by RNA polymerases II and III, respectively. While the p53 tumor suppressor protein is a general repressor of RNA polymerase III transcription, whether p53 regulates snRNA gene transcription by RNA polymerase II is uncertain. The data presented herein indicate that p53 is an effective repressor of snRNA gene transcription by both polymerases. Both U1 and U6 transcription in vitro is repressed by recombinant p53, and endogenous p53 occupancy at these promoters is stimulated by UV light. In response to UV light, U1 and U6 transcription is strongly repressed. Human U1 genes, but not U6 genes, contain a high-affinity p53 response element located within the core promoter region. Nonetheless, this element is not required for p53 repression and mutant p53 molecules that do not bind DNA can maintain repression, suggesting a reliance on protein interactions for p53 promoter recruitment. Recruitment may be mediated by the general transcription factors TATA-box binding protein and snRNA-activating protein complex, which interact well with p53 and function for both RNA polymerase II and III transcription.

ACKNOWLEDGMENTS

The anti-galectin-3 antibody (Mac2) was a gift from John Wang (Michigan State University). The pRc/RSV and pRc/RSV-p53-Flag.wt plasmids were a gift from Roland Kwok (University of Michigan). We thank Liping Gu, Gauri Jawdekar, Min-Hao Kuo, and Jim Geiger for critical assessment of the manuscript and appreciate the technical assistance provided by Craig Hinkley, Brandon LaMere, Xianzhou Song, and Tharakeswari Selvakumar. We acknowledge the National Cell Culture Center for preparation of HeLa cells.

This work was supported by an NIH grant (GM59805) to R.W.H.