Multiple Variant mRNAs with Different Length Tandem Repeats of (CAYYCC)n Produced from Bovine Selenoprotein P-like Protein Gene

ABSTRACT

In contrast to selenoprotein Ps (SelPs) from other animal species, bovine selenoprotein P-like-protein (SelPLP) was found to contain a tandem repeat of (CAYYCC)11. During an investigation into whether SelPLP was a bovine substitute for SelP or uniquely bovine, its mRNA was found to consist of multiple variants with different length tandem repeat, namely p(0) with (CAYYCC)11, p(-4) lacking (CAYYCC)4, p(-8) lacking (CAYYCC)8, and p(-9) lacking (CAYYCC)9. Although they were encoded on a single gene locus, neither classical GT-AG nor minor class AT-AC donator-acceptor sequences for alternative splicing were identified. A subsequent S1 protection assay using oligonucleotides, whose sequence may occur as variants, performed against bovine poly(A)+RNA identified a total of nine variants. Judging from the sequence of these variants and the branch point mapping, the consensus sequence for recognition of the donator was CACCCCCAC and of the acceptor and the branch point A nucleotide, ACCCCCAT or ACCCCCATCCCCAT. Furthermore, when the p(0) insert mRNA was expressed in COS-7 cells derived from an African green monkey kidney, cDNAs corresponding to p(-8) and p(-9) could be isolated. Therefore, the bovine SelPLP mRNAs consisted of multiple variants probably due to a novel splicing mechanism which was not bovine-specific but common to other mammals.