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G Shumyatsky

Publications and source records attributed to G Shumyatsky.

5 recordsLinked to original sources
PubMed1997

Formation of 2',3'-cyclic phosphates at the 3' end of human U6 small nuclear RNA in vitro. Identification of 2',3'-cyclic phosphates at the 3' ends of human signal recognition particle and mitochondrial RNA processing RNAs.

Approximately 90% of human U6 small nuclear RNA (snRNA) contains uridine cyclic phosphate (U>p) at its 3'-end (Lund, E., and Dahlberg, J. E. (1992) Science 255, 327-330). We studied the formation of U>p at the 3' end of human U6 snRNA using an in vitro system where uridylic acid residues are added from UTP precursor and U>p is formed. Analysis of U6 snRNAs with varying number of uridylic acid residues showed that each of these species contains U>p where the phosphate originated from alpha-phosphate of UTP precursor. The cyclic phosphate formation occurred on U6 snRNA in extracts where essential spliceosomal snRNAs were specifically degraded, thereby indicating that U>p formation is not coupled to pre-mRNA splicing. A subpopulation of human signal recognition particle and mitochondrial RNA processing RNAs isolated from HeLa cells also contained cyclic phosphates at their 3' ends. These data suggest that U>p in U6 snRNA is unlikely to be related to its participation in splicing of pre-mRNAs. It appears that cyclic phosphate is an intermediate product in the metabolism of these small RNAs.

HeLa Cells↗
PubMed1994

Capping signals correspond to the 5' end in four eukaryotic small RNAs containing gamma-monomethylphosphate cap structure.

In eukaryotic cells, the gamma-monomethylphosphate cap structure has been identified in four small RNAs, namely, U6, 7SK, B2, and plant U3 RNAs. In this study, we show that in the case of 7SK and B2, as well as in plant U3 RNAs, the 5' stem-loop followed by a short single-stranded region serves as the capping signal. We previously showed that the nucleotides 1-25 of mouse U6 snRNA, also comprised of a stem-loop followed by a short single-stranded region, function as the capping signal. These data show that capping signals in all four RNAs have common features. The length of the stem-loop among these capped RNAs varied from 20 to 108 nucleotides, with no significant variation in the capping efficiency. In addition to the capping signal, we also observed a minimum RNA length requirement of about 15-25 nucleotides following the stem-loop for efficient capping in vitro. The capping signal in plant U3 snRNA corresponds to the additional 5' stem-loop found in U3 RNAs from plants and lower eukaryotes but absent in U3 RNA from higher animals. Consistent with this observation, the human U3 RNA that lacks the additional 5' stem-loop was not a suitable substrate for capping when compared to U6 snRNA.

Animals↗
PubMed1993

Methylphosphate cap structure increases the stability of 7SK, B2 and U6 small RNAs in Xenopus oocytes.

We studied the role of the methylphosphate cap structure in the stability and nucleocytoplasmic transport by microinjecting U6, 7SK and B2 RNAs into the Xenopus oocytes. In every case, the methylphosphate capped RNAs were 3 to 9 times more stable than the uncapped RNAs. When a methylphosphate cap structure was placed on human H1 RNA which is normally not capped, its stability was improved 2-7 fold. These data show that the methylphosphate cap enhances the stability of 7SK, B2, H1 and U6 RNAs. The methylphosphate-capped 7SK RNA was transported into the nucleus from cytoplasm, but remained in the nucleus when injected into the nucleus; in this respect, 7SK RNA exhibited properties previously shown for U6 RNA. Both U6 and 7SK RNAs with ppp on their 5' ends were transported from cytoplasm to the nucleus suggesting that the methylphosphate cap structure is not required for transport of these RNAs across the nuclear membrane.

Animals↗
PubMed1992

Compilation of small RNA sequences.

This is an update containing small RNA sequences published during 1991. Approximately two hundred small RNA sequences are available in this and earlier compilations. The hard copy print out of this set will be available directly from us (inquiries should be addressed to R. Reddy). These files are also available on GenBank computer. Sequences from various sources covered in earlier compilations (see Reddy, R. Nucl. Acids Res. 16:r71; Reddy, R. and Gupta, S. Nucl Acids Res. 1990 Supplement, 18:2231 and 1991 Supplement, 19:2073) are not included in this update but are listed below.

Animals↗