Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.4 (RNase H)
 2,751 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A key transferase in the generation of mature N-linked carbohydrates is the medial Golgi enzyme N-acetylglucosaminyltransferase I (EC 2.4.1.101; GlcNAc-TI) which is encoded by the Mgat-1 gene. Previous studies revealed two size classes of Mgat-1 mRNA that are differentially expressed in mouse tissues. Nearly all tissues possess a shorter form (approximately 2.9 kb), whereas brain has predominantly a longer Mgat-1 mRNA (approximately 3.3 kb). We now show, by in situ hybridization of horizontal sections of adult mouse brain, that Mgat-1 RNA levels vary markedly in different brain cell types with the greatest expression being in neuronal cells. The differential expression of the approximately 2.9 kb and approximately 3.3 kb Mgat-1 mRNAs is likely to be controlled by tissue-specific promoters since the size difference between the mRNAs was found to residue entirely in the 5' untranslated region of the approximately 3.3 kb mRNA. Evidence for this was obtained by an RNase H strategy, reverse transcription-polymerase chain reaction (RT-PCR) and 5' anchored PCR. All of the 0.4 kb difference in size was localized upstream of the previously isolated cDNA sequence. Sequence information from this region was obtained from a mouse brain cDNA library by a PCR amplification strategy and a probe specific for the 3.3 kb mRNA was generated. This probe hybridized uniquely to the approximately 3.3 kb Mgat-1 mRNA and Southern blot analysis showed that the new sequence is physically linked to the Mgat-1 gene. A tissue culture model which displays an increase in expression of the approximately 3.3 kb Mgat-1 mRNA transcript during differentiation to neuronal cells has been developed in P19 embryonal carcinoma (EC) cells. The combined data suggest that 5' exons in the Mgat-1 gene are differentially utilized by tissue-specific promoters and that transcription factor(s) which specify production of the approximately 3.3 kb Mgat-1 mRNA are induced by retinoic acid treatment of P19 EC cells.
 ...
PMID:Regulation of N-linked glycosylation. Neuronal cell-specific expression of a 5' extended transcript from the gene encoding N-acetylglucosaminyltransferase I. 788 Nov 85

Numerous eukaryotic mRNAs contain sequences complementary to segments of the 18S and 28S rRNAs. Previous studies raised the possibility that these complementarities might allow mRNA-rRNA interactions and affect rates of translation. In the present study, we investigated the mRNA encoding the mouse Gtx homeodomain protein. This mRNA contains within its 5' untranslated region (UTR) a segment that is complementary to two regions of the 18S rRNA, located at nucleotides 701-741 and 1104-1136. A Gtx RNA probe containing this complementarity could be photochemically cross-linked to ribosomal subunits through a linkage to 18S rRNA but not to 28S rRNA. Oligonucleotide-directed RNase H digestion of the rRNA and a reverse transcription analysis localized the cross-linked probe to the complementary segment of 18S rRNA at nucleotides 1104-1136 but not at nucleotides 701-741. To determine whether complementarity in the Gtx mRNA affected translation, a mutational analysis was performed with a Gtx-luciferase fusion construct and four related constructs with altered complementarity to the 18S rRNA. These constructs were examined for their ability to be translated in cell-free lysates prepared from P19 embryonal carcinoma and C6 glioma cell lines and after cellular transfection into these same cell lines. In both cell-free translation and transfection studies, the rate of translation decreased more than 9-fold as the degree of complementarity to nucleotides 1104-1136 of the 18S rRNA increased. We hypothesize that segments complementary to rRNA, such as those contained within the Gtx mRNA, form a category of cis-acting regulatory elements in mRNAs that affect translation by base pairing to rRNA within ribosomes.
 ...
PMID:rRNA-complementarity in the 5' untranslated region of mRNA specifying the Gtx homeodomain protein: evidence that base- pairing to 18S rRNA affects translational efficiency. 999 25