Alternative Splicing of pre-mRNA encoding the Musca domestica Latrophilin-Like Protein: Primary structures of four spliced forms of mRNA and their protein products


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Abstract

An internal DNA fragment (∼2000 bp) homologous to the conserved regions of genes encoding latrophilin-like proteins (LLPs) was obtained by the PCR technique using degenerate primers to these gene regions. The gene-specific primers were synthesized based on the results of sequencing of the isolated fragment, and all overlapping cDNA fragments of the llp gene encoding the Musca domestica LLP were obtained by the rapid amplification of cDNA 5′- and 3′-ends (5′- and 3′-RACE). Four alternatively spliced mRNAs were found while sequencing the obtained cDNA fragments. Two long mRNAs (∼6000 nt) differ in the structures of both the regions encoding signal peptides and 5′-terminal untranslated regions. They encode large proteins (∼1800 aa), whose domain organization is similar to that of mammalian latrophilins. Each deduced protein contains a domain with seven transmembrane strands followed by an extended cytoplasmic C-terminal domain. Two other mRNA forms are derived from these long mRNAs; they encode proteins severely truncated at their C-termini (∼900 aa). They are composed of the domain with only three transmembrane regions and a short unique cytoplasmic C-terminal domain (23 aa). The limitations and drawbacks of the existing 3′-RACE techniques found during study of the long alternatively spliced cDNAs are analyzed, and ways for overcoming these difficulties are proposed.

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