GSBS Student Publications

Title

Cell cycle dependent phosphorylation and subnuclear organization of the histone gene regulator p220(NPAT) in human embryonic stem cells

GSBS Program

Biochemistry & Molecular Pharmacology

UMMS Affiliation

Graduate School of Biomedical Sciences; Department of Cell Biology and Cancer Center

Date

5-24-2007

Document Type

Article

Medical Subject Headings

Cell Cycle; Cell Cycle Proteins; Cell Line; Coiled Bodies; Cyclins; Diatrizoate; Embryonic Stem Cells; Ficoll; Gene Expression Regulation; Humans; Nuclear Proteins; Phosphorylation

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

Human embryonic stem (ES) cells have an expedited cell cycle ( approximately 15 h) due to an abbreviated G1 phase ( approximately 2.5 h) relative to somatic cells. One principal regulatory event during cell cycle progression is the G1/S phase induction of histone biosynthesis to package newly replicated DNA. In somatic cells, histone H4 gene expression is controlled by CDK2 phosphorylation of p220(NPAT) and localization of HiNF-P/p220(NPAT) complexes with histone genes at Cajal body related subnuclear foci. Here we show that this 'S point' pathway is operative in situ in human ES cells (H9 cells; NIH-designated WA09). Immunofluorescence microscopy shows an increase in p220(NPAT) foci in G1 reflecting the assembly of histone gene regulatory complexes in situ. In contrast to somatic cells where duplication of p220(NPAT) foci is evident in S phase, the increase in the number of p220(NPAT) foci in ES cells appears to precede the onset of DNA synthesis as measured by BrdU incorporation. Phosphorylation of p220(NPAT) at CDK dependent epitopes is most pronounced in S phase when cells exhibit elevated levels of cyclins E and A. Our data indicate that subnuclear organization of the HiNF-P/p220(NPAT) pathway is rapidly established as ES cells emerge from mitosis and that p220(NPAT) is subsequently phosphorylated in situ. Our findings establish that the HiNF-P/p220(NPAT) gene regulatory pathway operates in a cell cycle dependent microenvironment that supports expression of DNA replication-linked histone genes and chromatin assembly to accommodate human stem cell self-renewal.

Rights and Permissions

Citation: J Cell Physiol. 2007 Oct;213(1):9-17. Link to article on publisher's site

DOI of Published Version

10.1002/jcp.21119

Related Resources

Link to article in PubMed

Journal Title

Journal of cellular physiology

PubMed ID

17520687