A histone 3' end processing machinery in protozoa

• In metazoa replication-dependent histone mRNAs are not polyadenylated. At the 3' end of these mRNAs there is a conserved sequence that contains a 16 nucleotide stem loop (SL) besides a purine rich sequences, called the histone downstream element (HDE) located several nucleotides downstream. This is necessary for endonucleolytic cleavage of pre-mRNA to release the mature mRNA. For this task also trans-acting factors are needed, such as a U7 snRNP, a stem loop binding protein (SLBP) and a subunit of the cleavage/polyadenylation specificity factor (CPSF-73)1,2. In order to understand the evolutionary origin of this molecular machinery we have computationally searched for all the transacting factors as well as the histone mRNA stem-loop structure in histone mRNAs in a range of eukaryotic species. We have used profile HMMs and covariance models to identify SL motifs as well as U7 RNA homologues in lower metazoa. Profile-based searches were used to identify proteins homologous to the mammalian SLBP. Surprisingly, a number of protozoan species seem to have the histone 3' end processing machinery characteristic of metazoa. These results show that this machinery is more ancient than previously anticipated.

Ämnesord

NATURVETENSKAP  -- Biologi -- Bioinformatik och systembiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Bioinformatics and Systems Biology (hsv//eng)

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