Low dose ionizing radiation-induced activation of connexin 43 expression.
OBJECTIVE
Connexin 43 has been implicated in the cellular response to ionizing radiation by enabling cell-to-cell communication. It is established here that the expression of connexin 43 is affected by ionizing radiation and the mechanism involved is investigated.


METHODS
The human connexin 43 promoter was cloned into a Luciferase reporter plasmid and activation by ionizing radiation was measured in normal human fibroblasts as well as HeLa cells. The regions responsible for the radiation inducibility were defined using deletion and point mutations of the construct. The results were confirmed by Northern and Western blotting.


RESULTS
Ionizing radiation activates the human connexin 43 promoter in a time- and dose-dependent manner with a maximal induction (4.2-fold +/-0.58) after 6 h and a dose of 0.5 Gy. Higher doses up to 5 Gy led to a less marked increase (2-fold) over the same period. This promoter activation was associated with comparable increases in both connexin 43 mRNA and protein levels. The low dose radiation response of the promoter is mainly dependent on consensus binding sites for nuclear factor of activated T-cells (NFAT) and activator protein (AP1) in a region -2537 and -2110 bp from the transcriptional start site as determined by mutation analysis.


CONCLUSIONS
Low doses of ionizing radiation induce the transcriptional upregulation of connexin 43 expression employing NFAT and AP1 sites.
Glover
D
D
Queensland Institute of Medical Research, Herston, Australia.
Little
J B
JB
Lavin
M F
MF
Gueven
N
N
D000595:Amino Acid Sequence; D018031:Connexin 43 / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000378:metabolism* / Q000528:radiation effects*; D005786:Gene Expression Regulation / Q000528:radiation effects*; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D011829:Radiation Dosage; D011839:Radiation, Ionizing; D020539:Sequence Analysis, Protein; D015533:Transcriptional Activation / Q000528:radiation effects*; D015854:Up-Regulation / Q000528:radiation effects
D018031:Connexin 43