Characterization of the chicken inward rectifier K+ channel IRK1/Kir2.1 gene.
BACKGROUND
Inward rectifier potassium channels (IRK) contribute to the normal function of skeletal and cardiac muscle cells. The chick inward rectifier K+ channel cIRK1/Kir2.1 is expressed in skeletal muscle, heart, brain, but not in liver; a distribution similar but not identical to that of mouse Kir2.1. We set out to explore regulatory domains of the cIRK1 promoter that enhance or inhibit expression of the gene in different cell types.


RESULTS
We cloned and characterized the 5'-flanking region of cIRK1. cIRK1 contains two exons with splice sites in the 5'-untranslated region, a structure similar to mouse and human orthologs. cIRK1 has multiple transcription initiation sites, a feature also seen in mouse. However, while the chicken and mouse promoter regions share many regulatory motifs, cIRK1 possesses a GC-richer promoter and a putative TATA box, which appears to positively regulate gene expression. We report here the identification of several candidate cell/tissue specific cIRK1 regulatory domains by comparing promoter activities in expressing (Qm7) and non-expressing (DF1) cells using in vitro transcription assays.


CONCLUSIONS
While multiple transcription initiation sites and the combinatorial function of several domains in activating cIRK1 expression are similar to those seen in mKir2.1, the cIRK1 promoter differs by the presence of a putative TATA box. In addition, several domains that regulate the gene's expression differentially in muscle (Qm7) and fibroblast cells (DF1) were identified. These results provide fundamental data to analyze cIRK1 transcriptional mechanisms. The control elements identified here may provide clues to the tissue-specific expression of this K+ channel.
Mutai
Hideki
H
Department of Pathology and Laboratory Medicine, Division of Neuropathology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA. Hideki_Mutai@meei.harvard.edu <Hideki_Mutai@meei.harvard.edu>
Kenyon
Lawrence C
LC
Locke
Emily
E
Kikuchi
Nami
N
Oberholtzer
John Carl
JC
D024506:5' Flanking Region / Q000235:genetics; D000818:Animals; D030161:Avian Proteins / Q000235:genetics; D001483:Base Sequence / Q000235:genetics; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D002645:Chickens / Q000235:genetics*; D003001:Cloning, Molecular / Q000379:methods; D005819:Genetic Markers / Q000235:genetics; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism; D009206:Myocardium / Q000737:chemistry / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry* / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D016385:TATA Box / Q000235:genetics; D024363:Transcription Initiation Site
D030161:Avian Proteins; D005819:Genetic Markers; C489461:Kir2.1 channel; D024661:Potassium Channels, Inwardly Rectifying