Characterization of the mRNAs encoding the gene 2 sarcoplasmic/endoplasmic-reticulum Ca2+ pump in pig smooth muscle.
The gene 2 sarcoplasmic/endoplasmic-reticulum (SR/ER) Ca2+ pump is expressed in slow skeletal and cardiac muscle, smooth muscle and non-muscle tissues. We have analysed the gene 2 Ca2+ pump mRNAs using a panel of anti-sense RNA probes which recognize either the muscle (class 1) or the non-muscle (class 2) transcript, or both. In pig smooth muscle, we confirmed the presence of the class 1 and class 2 mRNAs of 4.4 kb length and we also detected a third mRNA of 8.0 kb which reacted with both the class 1 and class 2 riboprobes. A 4.2 kb cDNA corresponding to the 3' part of the 8.0 kb mRNA was cloned from a pig gastric smooth muscle cDNA library. Nucleotide sequence analysis of this clone revealed that the 8.0 kb mRNA (class 3 transcript) contained both the non-muscle-specific and the muscle-specific exons separated by a 2.4 kb intron which has not been removed. The class 3-mRNA-encoded SR/ER Ca2+ pump is identical to the class 2-encoded non-muscle isoform. Northern blot analysis demonstrated that, in cardiac muscle, the class 1 mRNA (encoding the muscle isoform) is the predominant messenger, whereas in non-muscle tissues the class 2 and 3 mRNAs (encoding the non-muscle isoform) predominate. In smooth muscle all three mRNA types are present. The tissue distribution of the mRNA types suggests a tissue-dependent processing of the primary transcript of the sarcoplasmic/endoplasmic reticulum Ca2+ pump gene 2.
Eggermont
J A
JA
Laboratorium voor Fysiologie, K.U. Leuven, Belgium.
Wuytack
F
F
Casteels
R
R
D000818:Animals; D001483:Base Sequence; D001693:Biological Transport, Active; D015152:Blotting, Northern; D015220:Calcium Channels / Q000378:metabolism*; D004247:DNA / Q000032:analysis; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics*; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D013552:Swine; D014158:Transcription, Genetic
D015220:Calcium Channels; D012333:RNA, Messenger; D004247:DNA