Sm Y-10 is found in the same fractions as the SL snRNPs (at 200 kDa), indicating Sm Y-10 is present in smaller complexes than the other Sm Y family members. the SL1 RNA/Sm/SL75p/SL21p complex, the Sm Y/Sm/SL75p/SL26p complex is usually associated with there are two functionally distinct SL RNAs. SL1 RNA is used to replace the outron. The other, SL2 RNA, is used for splicing polycistronic pre-mRNAs (Spieth et al. 1993). Many genes are contained in operons, multigene transcription units that are coregulated from a single promoter at the 5 end of the cluster. These polycistronic pre-mRNAs are processed into single-gene, mature, capped, polyadenylated mRNAs by a process involving both 3-end formation at the poly(A) sites of upstream genes and SL snRNP to homologs of the SL-specific proteins in an effort to determine how SL1 and SL2 snRNPs function in different contexts. We demonstrate that whereas the SL1 snRNP contains a complex consisting of the SL75p/SL21p proteins that are homologs of the SL snRNP proteins, the SL2 snRNP does not. Instead, we make the surprising discovery that SL26p, a paralog of SL21p, is usually complexed with SL75p, and SL75p/SL26p is bound to a different family of novel snRNAs, the Sm Y snRNAs, initially discovered in (Maroney et al. 1996). We show that SL21p and SL26p nonetheless have a synthetic phenotype, and we present a model, involving base pairing of SL RNAs to Sm Y, to account for how these proteins could ADX-47273 be associated with different classes of snRNAs and yet be involved ADX-47273 in the same process. RESULTS Homologs of the SL proteins The genome contains three genes homologous to the SL-specific proteins identified by the Nilsen laboratory (Denker et al. 2002): SL75p is usually homologous to SL95p, and SL21p and SL26p are homologous to SL30p. The gene for SL26p is called and and the related species (estimated to be 100 million years diverged from sequence shares more similarity with the smaller protein, SL21p, than it does with the larger one, SL26p. This is expected based on the presence of SL21p in the SL1 snRNP (see below), since the SL RNA is a close relative of SL1 RNA. The N-terminal regions of all five sequences contain two repeats of a novel motif, with a consensus sequence Y(N/A)DYVX(R/Q)FEQW(K/E) (strong underlined in Fig. 1). These repeats are candidates for conversation with SL75p since each of the SL30p family members interacts with SL75p (see ADX-47273 below). Open in a separate window Physique 1. Alignment of SL30p with SL21p and SL26p from and SL30p sequence is usually from UniProt (Q8T3T6_ASCSU). SL21p and SL26p are encoded by W02F12.6, homolog sequences were obtained from Wormbase. The five sequences were aligned using Clustal W. ADX-47273 As: and protein is fairly well conserved with SL21p, but very different from SL26p. The SL26p Rabbit Polyclonal to DNAI2 sequence is much more highly conserved between and in this region than is usually SL21p, but it is quite different from the SL30p or SL21p (underlined in Fig. 1). These sequences are candidates for conversation with a protein or RNA with which ADX-47273 SL26p interacts, but SL21p does not. The Sm Y family A novel RNA, called Sm Y, associated with spliceosomal preparations from extract, was identified in the Nilsen laboratory (Maroney et al. 1996). This RNA is usually predicted to fold into two stems separated by a single-stranded region made up of a canonical Sm-binding site. The Sm Y was shown to be Sm protein bound, and we demonstrate below that this Sm Y RNAs are also Sm snRNPs. We identified a 12-gene family in the genome that specifies Sm Y, along with 10 homologs in the genome. A dendrogram showing the relationship between these genes is usually shown in Physique 2. As in the SL2 RNA gene family (see below), a few common genes in the last common ancestor of and radiated to form the gene families of today. Importantly, our phylogenetic analysis indicates that there is a single evolutionarily distinct member of the gene family, Sm Y-10, in both species. The RNA specified by this gene behaves quite differently from other family members, as shown below. Previously published work designed to uncover new small RNA species in has shown that many of the family members are expressed (Deng et al. 2006; He et al. 2006), and our data confirm that RNAs specified by most or all of the genes can be detected with varying levels of expression at different developmental stages (data not shown). The Sm Y RNAs range in size from 77 to 82 nt with the exception of Sm Y-10, which is distinctly larger, 88 nt. Open in a separate window Physique 2. The.