Human transformer 2beta and SRp55 interact with a calcitonin-specific splice enhancer.
The calcitonin/calcitonin gene-related peptide (CGRP) pre-mRNA is alternatively processed in a tissue-specific manner leading to the production of calcitonin mRNA in thyroid C cells and CGRP mRNA in neurons. Sequences in the human calcitonin-specific fourth exon function as an exonic splice enhancer (ESE) which is required for incorporation of exon 4 into calcitonin mRNA. Deletion of these sequences from the rat calcitonin/CGRP gene was reported to have no effect on calcitonin splicing. We demonstrate that sequences in the rat calcitonin/CGRP fourth exon act as an ESE. In addition, we observed that three proteins in HeLa nuclear extract, of apparent molecular weights of 40, 55 and 85 kDa, specifically interact with the exon 4 ESE. The 40-kDa protein is human transformer 2beta (hTra2beta), a homolog of the Drosophila splice regulator transformer 2. hTra2beta is required for calcitonin splicing in vitro, one of the first biological functions identified for hTra2beta. The 55-kDa protein is SRp55, a member of the SR family of phosphoproteins. Binding of SRp55 to an ESE required for calcitonin mRNA splicing suggests that the different levels of SRp55 present in different cell types may regulate calcitonin/CGRP alternative splicing.
Tran
Quincy
Q
Department of Biochemistry and Molecular Biophysics, Virginia Commonwealth University, 1101 E. Marshall Street, Richmond, VA 23298, USA.
Coleman
Timothy P
TP
Roesser
James R
JR
D000818:Animals; D002116:Calcitonin / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D015740:Calcitonin Gene-Related Peptide / Q000096:biosynthesis / Q000235:genetics*; D002478:Cells, Cultured; D004742:Enhancer Elements, Genetic; D005091:Exons; D006367:HeLa Cells; D006801:Humans; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism; D012326:RNA Splicing; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D051381:Rats; D000068103:Serine-Arginine Splicing Factors; D013961:Thyroid Gland / Q000378:metabolism; D014162:Transfection
D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012322:RNA Precursors; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C097083:TRA2B protein, human; C490770:Tra2b protein, rat; D000068103:Serine-Arginine Splicing Factors; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide