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Updated: Jul 19, 2026

Proliferation and Differentiation of Murine Myeloid Precursor 32D/G-CSF-R Cells
Published on: February 21, 2018
Early growth response transcription factor EGR-1 regulates Galphaq gene in megakaryocytic cells
G Jalagadugula1, D N Dhanasekaran, S Kim
1Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Background:
Galphaq (Gene GNAQ) plays a major role in platelet signal transduction but little is known regarding its transcriptional regulation.
Objectives:
We studied Galphaq promoter activity using luciferase reporter gene assays in human erythroleukemia (HEL) cells treated with phorbol 12-myristate 13-acetate (PMA) for 24 h to induce megakaryocytic transformation.
Methods And Results:
PMA-treated HEL cells showed enhanced Galphaq expression. Reporter (luciferase) gene studies on 5' upstream construct (up to -116 bp from ATG) revealed a negative regulatory site at -238/-202 and two positive sites at -203/-138 and -1116/-731. The positive regulatory region -203/-138 contained overlapping Sp1/AP-2/EGR-1 consensus sites. Gel shift studies on Galphaq oligonucleotides 1 (-203/-175) and 2 (-174/-152) using HEL cell extracts demonstrated protein binding that was due to early growth response factor EGR-1 at two sites. Mutations in either EGR-1 site markedly decreased the gene activity, indicating functional relevance. Mutation of consensus E-Box motif (-185/-180) had no effect. Reduction in the expression of endogenous EGR-1 with antisense oligonucleotide to EGR-1 inhibited PMA-induced Galphaq transcription. Correspondingly, Egr-1 deficient mouse platelets also showed approximately 50% reduction in the Galphaq expression relative to wild-type platelets.
Conclusions:
These studies suggest that Galphaq gene is regulated during PMA-induced megakaryocytic differentiation by EGR-1, an early growth response transcription factor that regulates a wide array of genes and plays a major role in diverse activities, including cell proliferation, differentiation and apoptosis, and in vascular response to injury and atherosclerosis.
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