Alternative 5' exons and differential splicing regulate expression of protein 4.1R isoforms with distinct n-termini

Journal Article · Tue Mar 25 04:00:00 EST 2003 · Blood

DOI:https://doi.org/10.1182/blood-2002-06-1796· OSTI ID:810874

Parra, Marilyn K ^[1]; Gee, Sherry L; Koury, Mark J; Mohandas, Narla; Conboy, John G

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1. LBNL Library

Among the alternative pre-mRNA splicing events that characterize protein 4.1R gene expression, one involving exon 2' plays a critical role in regulating translation initiation and N-terminal protein structure. Exon 2' encompasses translation initiation site AUG1 and is located between alternative splice acceptor sites at the 5' end of exon 2; its inclusion or exclusion from mature 4.1R mRNA regulates expression of longer or shorter isoforms of 4.1R protein, respectively. The current study reports unexpected complexity in the 5' region of the 4.1R gene that directly affects alternative splicing of exon 2'. Three mutually exclusive alternative 5' exons, designated 1A, 1B, and 1C, were identified far upstream of exon 2 in both mouse and human genomes; all three are associated with strong transcriptional promoters in the flanking genomic sequence. Importantly, exons 1A and 1B splice differentially with respect to exon 2', generating transcripts with different 5' ends and distinct N-terminal protein coding capacity. Exon 1A-type transcripts splice so as to exclude exon 2' and therefore utilize the downstream AUG2 for translation of 80kD 4.1R protein, whereas exon 1B transcripts include exon 2' and initiate at AUG1 to synthesize 135kD isoforms. RNA blot analyses revealed that 1A transcripts increase in abundance in late erythroblasts, consistent with the previously demonstrated upregulation of 80kD 4.1R during terminal erythroid differentiation. Together these results suggest that synthesis of structurally distinct 4.1R protein isoforms in various cell types is regulated by a novel mechanism requiring coordination between upstream transcription initiation events and downstream alternative splicing events.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: USDOE Director, Office of Science. Office of Biological and Environmental Research. Life Sciences Division; National Institutes of Health (US)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 810874
• Report Number(s): LBNL--52397
• Journal Information: Blood, Journal Name: Blood; ISSN BLOOAW; ISSN 0006-4971
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ABUNDANCE
BONE MARROW CELLS
CAPACITY
EXONS
GENES
PROMOTERS
PROTEIN STRUCTURE
PROTEINS
RNA
SPLICING
SYNTHESIS
TRANSCRIPTION