GATA-1 DNA Binding Activity Is Down-regulated in Late S Phase in Erythroid Cells

Martin E Cullen,Roger K Patient

doi:10.1074/jbc.272.4.2464

Abstract

We have set out to test a model for tissue-specific gene expression that relies on the early replication of expressed genes to sequester limiting activating transcription factors. Using an erythroid cell line, we have tested the changes in the DNA binding activity of the lineage-restricted transcription factor GATA-1 through the cell cycle. We find that GATA-1 activity is low in G1, peaks in mid-S phase, and then decreases in G2/M. In contrast, the binding activities of two ubiquitous transcription factors, Oct1 and Sp1, remain high in G2/M. GATA-1 protein and mRNA vary in a similar manner through the cell cycle, suggesting that the expression of the gene or the stability of its message is regulated. Although a number of transcription factors involved in the control of the cell cycle or DNA replication have been shown to peak in S phase, this is the first example of a lineage-restricted transcription factor displaying S phase-specific DNA binding activity. One interpretation of these data leads to a model in which the peak in GATA-1 DNA binding amplifies the effect of early replication on the activation of erythroid-specific genes at the same time as preventing activation of non-erythroid genes containing GATA-responsive elements. These results may also relate to recent data implicating GATA-1 function in apoptosis and cell cycle progression.

Highlights

The relationship between cell division and differentiation is still unclear
The locus control region is required both for transcription and early replication of the ␤ globin locus [15], further maintaining the correlation between replication timing and tissue-specific gene activation, leading to a model where early replication removes repressive chromatin and allows activating transcription factors to bind [4, 16]
These considerations have led to the suggestion that fluctuations in the levels of critical transacting factors during S phase may amplify the effect on chromatin remodeling conferred by early replication [6]

Summary

Introduction

The relationship between cell division and differentiation is still unclear. In the hematopoietic system, it has long been thought that differentiation requires prior or concomitant cell division [1], but direct evidence for a mechanistic relationship has been hard to obtain. The cell cycle position of the peak in GATA-1 DNA binding activity was estimated by using the quantitative FACS data (see, for example, Fig. 1a).

Results

Conclusion