Cell Shape-dependent Regulation of Protein 4.1 Alternative Pre-mRNA Splicing in Mammary Epithelial Cells*
- P. Olivier Schischmanoff‡,
- Paul Yaswen,
- Marilyn K. Parra,
- Gloria Lee,
- Joel A. Chasis,
- Narla Mohandas and
- John G. Conboy§
- From the Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, the
- ‡ Laboratoire de Biochimie, CHU de Bicêtre, 94275 Le Kremlin-Bicêtre, France, and the Biochimie Metabolique et Clinique, Universite Paris V, 75006 Paris, France
- § To whom correspondence should be addressed: Life Sciences Division, Lawrence Berkeley National Laboratory, Bldg. 74-157, 1 Cyclotron Rd., Berkeley, CA 94720. Tel.: 510-486-6973; Fax: 510-486-6746.
Abstract
Expression of the complex gene encoding multiple isoforms of structural protein 4.1 is regulated by alternative pre-mRNA splicing. During erythropoiesis, developmental stage-specific inclusion of exon 16 generates protein 4.1 isoforms having a fully functional spectrin-actin binding domain. Here we show that human mammary epithelial cells (HMEC), coincident with the dramatic morphological changes induced by altered culture conditions, exhibit a novel pre-mRNA splicing switch involving a new exon (exon 17B, 450 nucleotides) in the COOH-terminal coding region. 4.1 RNA expressed in proliferating HMEC adherent to culture dishes mostly excluded exon 17B, whereas 4.1 transcripts processed in nondividing suspension cultures of HMEC strongly included this exon. This pre-mRNA splicing switch was reversible: cells transferred from poly(2-hydroxyethyl methacrylate) back to plastic resumed cell division and down-regulated exon 17B expression. More detailed studies revealed complex tissue-specific alternative splicing of exon 17B and another new exon 17A (51 nucleotides). These results predict the existence of multiple 4.1 protein isoforms with diverse COOH termini. Moreover, they strongly suggest that regulation of gene expression during differentiation of epithelial cells is mediated not only by transcriptional mechanisms, but also by post-transcriptional processes such as alternative pre-mRNA splicing.
Footnotes
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↵* This work was supported by National Institutes of Health Grants DK32094 and HL45182. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 The abbreviations used are:
- HMEC
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human mammary epithelial cell(s)
- E17A,E17B
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exon 17A and exon 17B, respectively
- poly-HEMA
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poly(2-hydroxyethyl methacrylate)
- RT
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reverse transcription
- PCR
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polymerase chain reaction.
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- Received August 14, 1996.
- Revision received January 17, 1997.
- © 1997 by The American Society for Biochemistry and Molecular Biology, Inc.
