Speaker: Wojtek Makalowski, University of Muenster 

Date: November 16 (Friday)

Place: 8th floor seminar room

Time: 11:00 am



Spliceosomal Small Nuclear RNA Genes of Insecta
The removal of introns from the primary transcripts of protein-coding genes is accomplished by the spliceosome, a large
macromolecular complex of which small nuclear RNAs (snRNAs) are crucial components. Following the recent sequencing
of the several insect genomes, we used various computational methods, ranging from sequence similarity search to
RNA secondary structure prediction, to search for putative snRNA genes (including their promoters) and to examine their
pattern of conservation among 17 available insect genomes (Apis mellifera, Tribolium castaneum, Bombyx mori, Anopheles
gambiae, Aedes aegypti, and twelve Drosophila species). We identified candidates for all nine spliceosomal snRNA genes in all the
analyzed genomes. All the species contain a similar number of snRNA genes, with the exception of A. aegypti, whose genome
contains more U1, U2, and U5 genes, and A. mellifera, whose genome contains fewer U2 and U5 genes. We found that snRNA
genes are generally more closely related to homologs within the same genus than to those in other genera. Promoter regions for
all spliceosomal snRNA genes within each insect species share similar sequence motifs that are likely to correspond to the PSEA
(proximal sequence element A), the binding site for snRNA activating protein complex, but these promoter elements vary in
sequence among the five insect families surveyed here. In contrast to the other insect species investigated, Dipteran genomes
are characterized by a rapid evolution (or loss) of components of the U12 spliceosome and a striking loss of U12-type introns.

Refrences
Mount, S.M., Gotea, V. Lin, C-F., Henandez, K. and Makalowski, W. (2007) Spliceosomal Small Nuclear RNA Genes in Eleven Insect Genomes.
 RNA, 13(1): 5-14

Drosophila Comparative Genome Sequencing and Analysis Consortium (2007) Genomics on a phylogeny: Evolution of Genes and Genomes in the Genus Drosophila.
 Nature, in press