Chromatin Assembly Factor-1, a Marker of Clinical Value to Distinguish Quiescent from Proliferating Cells

Abstract

Histone synthesis and chromatin assembly are mainly associated with DNA replication and are thus intimately involved in cell cycle regulation. The expression of key components involved in these events in human cells was studied in relation to cell-proliferative status. Among several chromatin assembly factors, chromatin assembly factor (CAF)-1 stood out as the most discriminating marker of the proliferative state. We show, using both immunofluorescence and Western blot analysis, that the expression of both CAF-1 large subunits, p150 and p60, is massively down-regulated during quiescence in several cell lines. Upon exit from the quiescent state, the CAF-1 subunits are re-expressed early, before DNA replication. The amounts of either total or chromatin-associated pools of CAF-1 proteins correlate directly with cell proliferation. Regulation of CAF-1 expression is partly controlled at the RNA level, as shown by quantitative reverse transcription-PCR and Northern blot experiments. Biological material from benign and malignant human breast tumors analyzed by immunocytochemistry and immunohistochemistry exhibits a strong positive correlation between CAF-1 p60 expression and the following proliferation markers: S-phase fraction (r ‫؍‬ 0.84, P < 0.0001); Ki-67 (r ‫؍‬ 0.94, P < 0.0001); and proliferating cell nuclear antigen (r ‫؍‬ 0.95, P ‫؍‬ 0.0001). We discuss the advantages of using CAF-1 to assess cell proliferation. High CAF-1 p60 levels are also shown to be associated with various prognostic factors. Our data highlight the precise association of CAF-1 expression with the proliferative state and validate the use of this factor as a useful proliferation marker and prognostic indicator in malignant and benign breast lesions.

The proliferation marker Chromatin Assembly Factor-1 is of clinical value in predicting the biological behaviour of salivary gland tumours

“…This was in-line with the reported association between the hyper-expression of the protein and the deregulation of the cell proliferation in malignant tumours of breast, tongue and prostate and in malignant melanoma, and was extremely significant in terms of statistical evaluation, besides tumour histotype, grade and stage at diagnosis (18,20).…”

“…Among these, the Chromatin Assembly Factor-1 (CAF-1), a heterotrimeric complex, composed of the histone-chaperone proteins p48, p60 and p150, is the most powerful discriminator between the proliferative and the quiescent state (15)(16)(17). CAF-1/p60 has been recently proposed as a new sensitive marker of cell proliferation, able to predict the prognosis of some human cancer types (18)(19)(20).…”

DNA Damage Leaves its Mark on Chromatin

“…An intriguing issue is whether such a repair-coupled chromatin assembly process still operates in a context where both CAF-1 and H3.1 levels are low, as observed in quiescent cells. 39,40 Given the high proportion of quiescent cells in an adult organism, this can be physiologically very important.…”

O-linked N -acetylglucosamine transferase (OGT) interacts with the histone chaperone HIRA complex and regulates nucleosome assembly and cellular senescence

“…The basic repeating unit of chromatin is the nucleosome (1), consisting of 147 base pairs of DNA wrapped around a core histone octamer composed of a central histone (H3-H4) 2 tetramer and two histone H2A-H2B dimers (2)(3)(4)(5). Nucleosome assembly is a key regulatory step in the establishment and maintenance of distinct chromatin states (4,(6)(7)(8), and deregulation of nucleosome assembly is linked to aging and cancer (4,9,10). Therefore, it is important to determine how nucleosome assembly pathways are regulated.…”