Activation of Protein Kinase C in Human Uterine Smooth Muscle Induces connexin-43 Gene Transcription through an AP-1 Site in the Promoter Sequence

doi:10.1074/jbc.271.39.23667

Activation of Protein Kinase C in Human Uterine Smooth Muscle Induces connexin-43 Gene Transcription through an AP-1 Site in the Promoter Sequence*

From the ^‡ Department of Obstetrics, Gynecology and Reproductive Medicine, School of Medicine, State University of New York, Stony Brook, New York 11794-8091, the
^§Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, Texas 77555-1062, and the
^¶Section of Molecular Cardiology, Department of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461

^∥To whom correspondence should be addressed. Tel.: 516-444-7708; Fax: 516-444-7740; E-mail: jandersen{at}epo.som.sunysb.edu

Abstract

Myometrial connexin-43 gap junctions are scarce throughout gestation but appear in large numbers at term to facilitate contractions during labor. The mechanisms that regulate this process are incompletely characterized. This report investigates the effects of protein kinase C activation on the regulation of connexin-43 gene transcription in human uterine smooth muscle cells. In primary myometrial cells treated with phorbol ester, transient increases in c-Fos and c-Jun protein levels were observed at 2-4 h, followed by significant increases in connexin-43 protein levels at 6-8 h. Nuclear run-on transcription analysis showed an increase in connexin-43 transcription 3 h after phorbol ester treatment. AP-1 sites were identified in the sequence of the 5′-flanking promoter region of the human connexin-43 gene at 44 and 1000 base pairs upstream of transcription start. Transcription from a reporter plasmid containing the proximal human connexin-43 promoter was increased in transfected primary cultures treated with phorbol ester. Mutation of the proximal AP-1 site in the promoter abolished the phorbol ester-dependent transactivation. This work provides evidence that transcription of the human connexin-43 gene is induced through protein kinase C activation in uterine smooth muscle cells, and that the induction involves up-regulation and activation of c-Jun and c-Fos.

Footnotes

↵* This work was supported in part by National Institutes of Health (NIH) Grant HD 30482 (to J. A.), a grant from the March of Dimes Birth Defects Foundation (to R. E. G.), and NIH Grant HL02391 (to G. I. F.). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) U64573[GenBank].
↵¹ The abbreviations used are:

PKC

protein kinase C

TPA

12-O-tetradecanoylphorbol-13-acetate

bp

base pair(s)

CAT

chloramphenicol acetyltransferase

ERE

estrogen response element

PRE

progesterone response element

HRE

hormone response element

ER

estrogen receptor.
- Received June 3, 1996.
- Revision received July 9, 1996.