Differences and similarities between Drosophila and mammalian 3' end processing of histone pre-mRNAs.
We used nuclear extracts from Drosophila Kc cells to characterize 3' end processing of Drosophila histone pre-mRNAs. Drosophila SLBP plays a critical role in recruiting the U 7 snRNP to the pre-mRNA and is essential for processing all five Drosophila histone pre-mRNAs. The Drosophila processing machinery strongly prefers cleavage after a fourth nucleotide following the stem-loop and favors an adenosine over pyrimidines in this position. Increasing the distance between the stem-loop and the HDE does not result in a corresponding shift of the cleavage site, suggesting that in Drosophila processing the U 7 snRNP does not function as a molecular ruler. Instead, SLBP directs the cleavage site close to the stem-loop. The upstream cleavage product generated in Drosophila nuclear extracts contains a 3' OH, and the downstream cleavage product is degraded by a nuclease dependent on the U 7 snRNP, suggesting that the cleavage factor has been conserved between Drosophila and mammalian processing. A 2'O-methyl oligonucleotide complementary to the first 17 nt of the Drosophila U 7 snRNA was not able to deplete the U 7 snRNP from Drosophila nuclear extracts, suggesting that the 5' end of the Drosophila U 7 snRNA is inaccessible. This oligonucleotide selectively inhibited processing of only two Drosophila pre-mRNAs and had no effect on processing of the other three pre-mRNAs. Together, these studies demonstrate that although Drosophila and mammalian histone pre-mRNA processing share common features, there are also significant differences, likely reflecting divergence in the mechanism of 3' end processing between vertebrates and invertebrates.
Dominski
Zbigniew
Z
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC 27599, USA. dominski@med.unc.edu
Yang
Xiao-Cui
XC
Purdy
Mathew
M
Marzluff
William F
WF
D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D004330:Drosophila / Q000166:cytology / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D012322:RNA Precursors / Q000235:genetics* / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D016601:RNA-Binding Proteins / Q000378:metabolism; D020885:Ribonucleoprotein, U7 Small Nuclear / Q000378:metabolism; D013379:Substrate Specificity
D029721:Drosophila Proteins; D006657:Histones; D012322:RNA Precursors; D016601:RNA-Binding Proteins; D020885:Ribonucleoprotein, U7 Small Nuclear; C490155:SLBP protein, Drosophila