Multiple alternate p21 transcripts are regulated by p53 in human cells

Abstract

The p53 tumor-suppressor is a transcription factor that is stabilized in response to cellular stress leading to growth arrest or apoptosis. p21 WAF1/CIP1 is a major transcriptional target of p53 and it plays a critical role in p53-dependent cell cycle arrest. In this study, we identified multiple alternate human p21 transcripts that have their transcriptional start sites in the direct proximity of the distal p53 response element. These transcripts are upregulated as a result of DNA damage-induced p53 activation. Furthermore, the basal expression of these alternate transcripts is strongly regulated by p53 and they are undetectable in p53-knocked down cells. This is in contrast to classical p21 transcripts, which have reduced, albeit detectable expression levels in the absence of p53. The existence of the alternate transcripts underscores the complexity of the human p21 genomic locus and opens up new avenues for further investigation.

A Novel Transcriptional Inhibitor Induces Apoptosis in Tumor Cells and Exhibits Antiangiogenic Activity

“…Also, HepG2 cell line with stable knock-down of p53 (HepG2-p53si; ref. 17) showed cleavage of caspase-3 confirming that ARC-mediated apoptosis is p53-independent (Fig. 4E).…”

“…MCF-7 and HepG2 cells with stable knock-down of p53 (MCF-7-p53si and HepG2-p53si, respectively) have been described previously (17). The cells were grown in different media as described (18).…”

Identification of a Chemical Inhibitor of the Oncogenic Transcription Factor Forkhead Box M1

“…Immunoblotting was done as described (18)(19)(20) with antibodies specific for p21 (556431; BD PharMingen, San Diego, CA), survivin (Santa Cruz Biotechnology, Santa Cruz, CA), cleaved caspase-3 (Cell Signaling Technology, Danvers, MA), and h-actin (Sigma-Aldrich, St. Louis, MO) antibodies. Immunoblot for FoxM1 was done using the previously generated rabbit antisera (2), and phospho-FoxM1 was detected using the MPM2 monoclonal antibody (Upstate Biotechnology, Lake Placid, NY), which recognizes the phosphorylated protein sequence phosphoserine/phosphothreonineproline.…”

TATA-binding Protein (TBP)-like Protein Is Required for p53-dependent Transcriptional Activation of Upstream Promoter of p21 Gene

“…Etoposide-treated Cellsp21 transcripts in MCF-7 cells are known to be increased by etoposide treatment (49). We examined p21 alt-1 transcripts from the chromosomal p21 gene in etoposide-treated HCT116 cells by RT-PCR.…”