Proliferation-Related Nucleolar Antigens P145 and P120 Associated with Separate Nucleolar Elements and Differences in Tissue Distribution

Abstract

Nucleolar antigens p145 and p120 are associated with proliferating cells (Freeman, J.W.; McRorie, D.K.; Busch, R.K.; Gyorkey, P.; Gyorkey, F.; Ross, B.E.; Spohn, W.H.; Busch, H. Cancer Res. 46:3593; 1986 and Freeman, J.W.; Busch, R.K.; Gyorkey, P.; Gyorkey, F.; Ross, B.E.; Busch, H. Cancer Res. 48:1244; 1988) and are not detectable in normal resting cells. Recent immunoelectron microscopic studies (Ochs, R.L.; Reilly, M.T.; Freeman, J.W.; Busch, H. Cancer Res. 48:6523; 1988) suggest that the two antigens have overlapping nucleolar localizations. In this study the nucleolus was physicochemically and biochemically studied to determine whether p145 and p120 were associated with a common nucleolar component. Antigen p145 was associated with 40-80 S ribonucleoprotein particles (RNPs), and the p145 antigen was not detected in HeLa cells following in situ RNAse digestion. P120 was found in a 40-80 S, RNAse resistant complex. Sequential extraction of HeLa nucleoli showed that most of antigen p145 was extractable in 10 mM Tris with 0.2% deoxycholate, whereas p120 was found in a nucleolar residue fraction requiring DNAse and high salt treatment for optimal extraction. Neither antigen p145 nor p120 was detectable in normal resting tissues. Antigen p145 was detected in all proliferating tissues examined, including a variety of malignant tumors (ten of ten), benign tissues including adenomas and hyperplasias (eight of eight), and in normal proliferating cells such as colonic epithelium and spermatogonia of the testes. Antigen p120 was not detected in all tumors, being absent in three of seven lymphomas and in one melanoma examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Nop2p Is Required for Pre-rRNA Processing and 60S Ribosome Subunit Synthesis in Yeast

“…p120 is a human proliferation marker that is predicted to function as a methylase (14,25). In this study, we demonstrate that Nop2p is required for synthesis of the 60S ribosomal subunit and processing of the 27S precursor to mature 25S and 5.8S rRNAs.…”

Expression of proliferation‐associated antigens (PCNA, p120, p145) during the reentry of G0 cells into the cell cycle

“…However, the recruitment of Go cells into the cycling compartment does appear to be one of many events associated with the overall oncogenic process, and its detection should be pursued with other relevant markers. There is a cascade of regulatory events during the recruitment process that includes, but is not limited to, the activation or down-regulation of suppressors (12,32,40), cyclins (22,23,33), proliferation-associated antigens (18,20,21), etc. To complicate an already complex picture, depending on the tumor type, these events do not always follow a certain chronology; however, when examined a s a whole, many of the events are directly involved in or associated with the control or up-regulation of cell proliferation.…”

Cell cycle regulated expression of nucleolar antigen P120 in normal and transformed human fibroblasts

“…P120 protein has been found to be localized to a novel microfibrillar structure of the nucleolar matrix (Ochs et al, 19881, and associated with DNA in the nucleolar residue in a large nucleoprotein particle which is resistant to RNase treatment (Freeman et al, 1989). This structure could play a role in cell cycle related alterations of the nucleolus and the nucleolar pleomorphism observed in tumor cells (Busch and Smetana, 1970).…”

“…Steady state levels of P120 mRNA have been determined in several cell lines and tumors. Tumor cells contained 15-60 times more P l Z O mRNA than normal cells (Hazlewood et al, 1989). Phytohemagglutinin-stimulated lymphocytes also contained more P120 mRNA than resting lymphocytes (Jhiang et al, 1990).…”