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MRNAs for plasma membrane calcium pump isoforms differing in their regulatory domain are generated by alternative splicing that involves two internal donor sites in a single exon.

ABSTRACT: cDNA clones coding for human plasma membrane Ca2+ pump isoforms have been isolated from a fetal skeletal muscle cDNA library. Compared with the sequence of a teratoma cDNA-encoded pump these clones specify isoforms that contain either 29- or 38-amino acid insertions within the calmodulin-binding region. Replacement of two basic arginine residues by an aspartic acid and a glutamine residue could influence the binding of calmodulin to these isoforms. RNase mapping shows that RNA species containing the 29-residue-encoding insertion are particularly abundant in skeletal muscles. The sequences coding for the insertions are present on a single 154-base-pair exon, as demonstrated by an analysis of the corresponding genomic region, and they are included in their respective mRNAs by alternative splicing involving the differential usage of two internal "cryptic" donor splice sites in the presence of a nearby canonical one. Inclusion of the complete 154-base-pair exon results in an mRNA coding for a pump protein with a shorter C-terminal amino acid sequence that lacks a consensus site for phosphorylation by the cAMP-dependent kinase. Exclusion, inclusion, or partial inclusion of the same exon can thus lead to the production of four different mRNAs from a single gene. When expressed as protein, these mRNAs encode Ca2+ pump isoforms that differ in their C-terminal regulatory domains.

SUBMITTER: Strehler EE

PROVIDER: S-EPMC297959 | biostudies-other | 1989 Sep

REPOSITORIES: biostudies-other

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mRNAs for plasma membrane calcium pump isoforms differing in their regulatory domain are generated by alternative splicing that involves two internal donor sites in a single exon.

Strehler E E EE Strehler-Page M A MA Vogel G G Carafoli E E

Proceedings of the National Academy of Sciences of the United States of America 19890901 18

cDNA clones coding for human plasma membrane Ca2+ pump isoforms have been isolated from a fetal skeletal muscle cDNA library. Compared with the sequence of a teratoma cDNA-encoded pump these clones specify isoforms that contain either 29- or 38-amino acid insertions within the calmodulin-binding region. Replacement of two basic arginine residues by an aspartic acid and a glutamine residue could influence the binding of calmodulin to these isoforms. RNase mapping shows that RNA species containing ...[more]

PMID: 2528729

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Project description:BackgroundTranscription factor 4 (TCF4 alias ITF2, E2-2, ME2 or SEF2) is a ubiquitous class A basic helix-loop-helix protein that binds to E-box DNA sequences (CANNTG). While involved in the development and functioning of many different cell types, recent studies point to important roles for TCF4 in the nervous system. Specifically, human TCF4 gene is implicated in susceptibility to schizophrenia and TCF4 haploinsufficiency is the cause of the Pitt-Hopkins mental retardation syndrome. However, the structure, expression and coding potential of the human TCF4 gene have not been described in detail.Principal findingsIn the present study we used human tissue samples to characterize human TCF4 gene structure and TCF4 expression at mRNA and protein level. We report that although widely expressed, human TCF4 mRNA expression is particularly high in the brain. We demonstrate that usage of numerous 5' exons of the human TCF4 gene potentially yields in TCF4 protein isoforms with 18 different N-termini. In addition, the diversity of isoforms is increased by alternative splicing of several internal exons. For functional characterization of TCF4 isoforms, we overexpressed individual isoforms in cultured human cells. Our analysis revealed that subcellular distribution of TCF4 isoforms is differentially regulated: Some isoforms contain a bipartite nuclear localization signal and are exclusively nuclear, whereas distribution of other isoforms relies on heterodimerization partners. Furthermore, the ability of different TCF4 isoforms to regulate E-box controlled reporter gene transcription is varied depending on whether one or both of the two TCF4 transcription activation domains are present in the protein. Both TCF4 activation domains are able to activate transcription independently, but act synergistically in combination.ConclusionsAltogether, in this study we have described the inter-tissue variability of TCF4 expression in human and provided evidence about the functional diversity of the alternative TCF4 protein isoforms.

Dataset Information

MRNAs for plasma membrane calcium pump isoforms differing in their regulatory domain are generated by alternative splicing that involves two internal donor sites in a single exon.

Publications

mRNAs for plasma membrane calcium pump isoforms differing in their regulatory domain are generated by alternative splicing that involves two internal donor sites in a single exon.

Similar Datasets

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