Reference Report

Reference
Citation	Gonsalvez, G.B., Praveen, K., Hicks, A.J., Tian, L., Matera, A.G. (2008). Sm protein methylation is dispensable for snRNP assembly in Drosophila melanogaster. RNA 14(5): 878--887. (Export to RIS)
FlyBase ID	FBrf0205403
Publication Type	Research paper
PubMed ID	18369183
PubMed Abstract	Sm proteins form stable ribonucleoprotein (RNP) complexes with small nuclear (sn)RNAs and are core components of the eukaryotic spliceosome. In vivo, the assembly of Sm proteins onto snRNAs requires the survival motor neurons (SMN) complex. Several reports have shown that SMN protein binds with high affinity to symmetric dimethylarginine (sDMA) residues present on the C-terminal tails of SmB, SmD1, and SmD3. This post-translational modification is thought to play a crucial role in snRNP assembly. In human cells, two distinct protein arginine methyltransferases (PRMT5 and PRMT7) are required for snRNP biogenesis. However, in Drosophila, loss of Dart5 (the fruit fly PRMT5 ortholog) has little effect on snRNP assembly, and homozygous mutants are completely viable. To resolve these apparent differences, we examined this topic in detail and found that Drosophila Sm proteins are also methylated by two methyltransferases, Dart5/PRMT5 and Dart7/PRMT7. Unlike dart5, we found that dart7 is an essential gene. However, the lethality associated with loss of Dart7 protein is apparently unrelated to defects in snRNP assembly. To conclusively test the requirement for sDMA modification of Sm proteins in Drosophila snRNP assembly, we constructed a fly strain that exclusively expresses an isoform of SmD1 that cannot be sDMA modified. Interestingly, these flies were viable, and snRNP assays revealed no defects in comparison to wild type. In contrast, dart5 mutants displayed a strong synthetic lethal phenotype in the presence of a hypomorphic Smn mutation. We therefore conclude that dart5 is required for viability when SMN is limiting.
DOI	10.1261/rna.940708
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Language of Publication	English
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Publication Type	Journal
Abbreviation	RNA
Title	RNA (New York, N.Y.)
Publication Year	1995-
ISBN/ISSN	1355-8382
Data from Reference
Alleles (12)
	Art7^NIG.9882R csul^e00797 csul^{Scer\UAS.T:Hsap\MYC} Scer\GAL4^da.G32 Scer\GAL4^tub.PU SmD1^{RK.Scer\UAS.P\T.T:Avic\GFP-YFP.Venus} SmD1^{Scer\UAS.P\T.T:Avic\GFP-YFP.Venus} SmD1^SH003 SmD1^{ΔRG.Scer\UAS.P\T.T:Avic\GFP-YFP.Venus} Smn^E33 T:Avic\GFP^YFP.Venus w^+mC
Constructs (7)
	P{GAL4-da.G32} P{NIG.9882R} P{tub-GAL4.U} P{UAS-csul-myc.G} P{UASp-VFP-SmD1.R-K} P{UASp-VFP-SmD1.ΔRG} P{UASp-VFP-SmD1}
Genes (27)
	Art7 csul Pcl Scer\GAL4 SmB SmD1 SmD3 Smn snRNA:U1:21D snRNA:U1:82Ea snRNA:U1:82Eb snRNA:U1:82Ec snRNA:U1:95Ca snRNA:U1:95Cb snRNA:U1:95Cc snRNA:U2:14B snRNA:U2:34ABa snRNA:U2:34ABb snRNA:U2:34ABc snRNA:U2:38ABa snRNA:U2:38ABb snRNA:U2:84Ca snRNA:U2:84Cb snRNA:U4:25F snRNA:U4:38AB snRNA:U4:39B w
Insertions (1)
	P{lacW}SmD1^SH003