P2P‐R protein localizes to the nucleolus of interphase cells and the periphery of chromosomes in mitotic cells which show maximum P2P‐R immunoreactivity

Abstract

P2P-R is a nuclear protein that can bind both p53 and Rb1. Its functions include roles in the control of RNA metabolism, apoptosis, and p53-dependent transcription. The expression of P2P-R also is repressed in G1 arrested terminally differentiated cells. The current studies therefore evaluated if P2P-R undergoes cell cycle-associated changes in its abundance and/or localization. Western blots show that relative to G0 quiescent cells, P2P-R protein levels are higher in populations of G2/M cells prepared by the physiological parasynchronization technique of serum deprivation followed by serum stimulation. More striking is the > 10-fold enrichment of P2P-R protein in specimens of highly purified mitotic cells prepared by the mitotic shake-select technique, or by synchrony with the mitotic spindle disruption agents nocodazole or vinblastine. These changes in P2P-R protein occur without a concomitant change in P2P-R mRNA expression suggesting that P2P-R immunoreactivity increases during mitosis. Confocal microscopy next established the localization of P2P-R to nucleoli in interphase cells and at the periphery of chromosomes in mitotic cells that lack nucleoli. The high levels of P2P-R localized to the periphery of chromosomes in mitotic cells suggest that P2P-R shares characteristics with other nucleolar proteins that associate with the periphery of chromosomes during mitosis. These include: nucleolin, B23, Ki67, and fibrillarin.

RBBP6 isoforms regulate the human polyadenylation machinery and modulate expression of mRNAs with AU-rich 3′ UTRs

“…In fact, the complex domain composition of RBBP6 suggests that the protein plays roles in multiple cellular events, perhaps functioning to integrate such pathways with premRNA processing. Indeed, RBBP6 has been reported to have roles in cell proliferation (Gao et al 2002) and differentiation (Witte and Scott 1997;), and RBBP6 levels are increased in a number of tumors (Yoshitake et al 2004;Motadi et al 2011;Chen et al 2013). In contrast to the behavior of full-length RBBP6, also known as iso1, iso3 is down-regulated in several tumors (Mbita et al 2012).…”

Association of genetic variants in the retinoblastoma binding protein 6 gene with the risk of glioma: a case-control study in a Chinese Han population

“…16 Furthermore, RBBP6 was strongly localized to chromosomes during mitosis and to nuclear speckles, which were believed to be the main sites of activity for pre-mRNA splicing and processing during interphase. 10,26 In short, these pieces of evidence meant that RBBP6 played a role in the regulation of these 2 proteins similar to that played by MDM2, 11 suggesting a possible model for the integra- * Adjusted for family history of cancer. Adj = adjusted.…”

“…8,10,19 Isoform 1 is encoded by a 6.1-kb transcript, and the alternative splicing of the 6.1-kb transcript results in isoform 2. Isoform 3 is encoded by a 1.1-kb transcript, which is also known as a domain with no name (DWNN).…”

Proliferation Potential-Related Protein, an Ideal Esophageal Cancer Antigen for Immunotherapy, Identified Using Complementary DNA Microarray Analysis

“…Both proliferation potential protein-related (P2P-R) and p53-associated cellular protein were reported to be mouse homologues of human PP-RP. P2P-R protein binds pRB (29) and colocalizes with chromosomes in mitotic cells (30).…”