Fig. 1. Domain patterns and tissue-specific differential splicing of MURF2. (A) Tissue-specific differential splicing of MURF2. RT-PCR demonstrates tissue-specific co-expression of multiple MURF2 transcripts. The 0.75 kb band of the 27 kDa isoform is detected only in cardiac muscle (arrowhead) but not in cDNA from adult skeletal muscle. Faint bands above 2 kb may represent further, yet unidentified isoforms. H, adult cardiac muscle; Sk, adult skeletal muscle; M, marker ladder, sizes given in kb. (B) MURF2 is expressed in four isoforms derived from differential splicing events. MURF2 isoforms of 27, 50 and 60 kDa are generated by sequential internal expansion of a core molecule containing the Ring, B-Box and C-terminal domain present in MURF2^p27. A third isoform, MURF2^p60B, is generated by the splicing of an additional exon before that of the C-terminal domain; a frameshift in the reading frame of this exon leads to the generation of an alternative C-terminus. (C) Generation of alternative C-termini in MURF2. Alternative splicing of the MURF2 gene that maintains the last exon (highlighted in red in B and C) while splicing in an additional 60 bp exon is observed in skeletal muscle. This leads to a frameshift in the last exon, omitting its reading frame and creating an alternative C-terminus (purple in B and C) which is fused directly to the Ser/Ala rich domain (blue in B and C). Note the alternative reading frame use in the last exon. The three C-terminal exons localise to a 20409 bp genomic region on chromosome 8q12, separated by introns of 1285 bp to 18762 bp. The large stretch of sequence between the last two exons may suggest the presence of further, as yet unidentified differentially spliced exons. In this figure, only the 3' region of the p60B isoform was mapped. The start of a new exon is indicated (^). Reading frames are numbered a, b and c, and the MURF2^p60B reading frame is shadowed in grey. Nucleotide numbering is according to our data library entry AJ431704.

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