Janet Stein, Ph.D.

Academic Role: Professor

Faculty Appointment(s) In:
   Cell Biology

Regulation of Gene Expression during the Cell Cycle and during the Proliferation/Differentiation Transition

Our laboratory is investigating the control of cell proliferation and its relationship to the onset and progression of differentiation. Our experimental approach is to examine molecular mechanisms involved in regulating specific genes that are expressed in actively proliferating cells, changes in the expression of these genes during the down-regulation of cell growth, and the initiation of expression of cell and tissue specific genes as cells differentiate.

One area of emphasis is the regulation of human histone gene expression. Histones are expressed primarily during the S phase of the cell cycle and are intimately involved with genome replication. We have focused on transcriptional regulation of the H4, H3 and H1 histone genes. In the H4 and H3 genes two sites of in vivo protein-DNA interaction have been identified in the proximal promoter region. Site I sequences influence the level of transcription while Site II sequences contain the cell cycle regulatory element and are also important for on/off regulation of this gene. We are continuing our characterization of the complex array of transcription factors and cell cycle regulatory proteins that bind these regulatory sequences to modulate expression both during the cell cycle and in the transition between proliferation and differentiation.

A second area of interest is the osteocalcin gene, which is normally expressed only in post-proliferative cells, primarily those of bone. We are investigating the many-faceted regulation of this gene both in terms of tissue-specificity and with regard to its activation as cells cease proliferating and assume a mature bone cell phenotype. The changes in chromatin structure and nuclear matrix association of the histone and osteocalcin genes that accompany changes in gene expression are being defined.

Figure

Regulation of histone gene expression during the cell cycle. Occupancy of the four principal regulatory elements of the histone H4 gene promoter is schematically illustrated during the S phase of the cell cycle when transcription is maximal (top panel) and during the G1/G2/mitotic periods of the cell cycle (middle panel). The lower panel illustrates complete loss of transcription factor complexes at Sites II, III and IV with the onset of differentiation. At this time transcription is completely downregulated.

Recent Publications

Vradii D, Zaidi SK, Lian JB, van Wijnen AJ, Stein JL, and Stein GS. 2005. Point mutation in AML1 disrupts subnuclear targeting, prevents myeloid differentiation, and effects a transformation-like phenotype.  Proc Natl Acad Sci U S A 102:7174-7179.

Miele A, Braastad CD, Holmes WF, Mitra P, Medina R, Xie R, Zaidi SK, Ye X, Wei Y, Harper JW, van Wijnen AJ, Stein JL, and Stein GS. 2005. HiNF-P directly links the cyclin E/CDK2/p220NPAT pathway to histone H4 gene regulation at the G1/S phase cell cycle transition.  Mol Cell Biol 25:6140-6153.

Paredes R, Arriagada G, Cruzat F, Villagra A, Olate J, Zaidi K, van WA, Lian JB, Stein GS, Stein JL, and Montecino M. 2004. Bone-specific transcription factor Runx2 interacts with the 1alpha,25-dihydroxyvitamin D3 receptor to up-regulate rat osteocalcin gene expression in osteoblastic cells.  Mol Cell Biol 24:8847-8861.

Gutierrez S, Liu J, Javed A, Montecino M, Stein GS, Lian JB, and Stein JL. 2004. The vitamin D response element in the distal osteocalcin promoter contributes to chromatin organization of the proximal regulatory domain.  J Biol Chem 279:43581-43588.

Mitra P, Xie RL, Medina R, Hovhannisyan H, Zaidi SK, Wei Y, Harper JW, Stein JL, van Wijnen AJ, and Stein GS. 2003. Identification of HiNF-P, a key activator of cell cycle-controlled histone H4 genes at the onset of S phase.  Mol Cell Biol 23:8110-8123.

Hovhannisyan H, Cho B, Mitra P, Montecino M, Stein GS, van Wijnen AJ, and Stein JL. 2003. Maintenance of open chromatin and selective genomic occupancy at the cell cycle-regulated histone H4 promoter during differentiation of HL-60 promyelocytic leukemia cells.  Mol Cell Biol 23:1460-1469.

Potential Rotation Projects

Project #1: HiNF-P in regulation of H4 histone gene transcription
HiNF-P is a critical factor that interacts with the proximal cell cycle regulatory element of the H4 histone gene. We have isolated a protein that possesses HiNF-P binding activity on the H4 promoter. This protein is a candidate for a key role in regulating H4 transcription during the cell cycle. To determine its biological activity, we will use molecular, biochemical and cellular approaches, including transfection and overexpression analyses coupled with immunofluorescence microscopy.

Project #2: Chromatin structure of an osteoblast-specific gene
Chromatin immunoprecipitation assays will be used to examine the dynamics of regulatory protein interactions with the promoter of the bone-related osteocalcin gene as expression is activated during osteoblast differentiation.

Academic Background

Ph.D., 1975, Princeton University

Office: S3-310
Phone: 508-856-4996
E-mail: Janet.Stein@umassmed.edu
Keywords: Stem Cell Biology, Cancer Biology, Cell Biology, Cell Cycle, Gene Regulation

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