Two conserved sequence blocks within eukaryotic tRNA genes are major promoter elements

Galli, Gabriella; Hofstetter, H.; Birnstiel, Max L.

doi:10.1038/294626a0

Cited by 458 publications

(281 citation statements)

References 34 publications

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“…This model would imply that, at least for this group of genes, transcriptionwould not require internal promotors present in each tRNA gene as has been demonstrated for several eukaryotic tRNAs (24,25,26); the synthesis of this group of tRNAs would actually involve, as in mitochondria from HeLa cells (27), the processing of longer transcripts.…”

Section: Discussionmentioning

confidence: 99%

Transcripts of mitochondrial tRNA genes inSaccharomyces cerevisiae

1982

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The transcription of a group of tRNA genes from the large tRNA gene cluster of mitochondrial DNA from Saccharomyces cerevisiae hase been investi gated by hybridization with DNA probes carrying t coding sequences and small portions of the A+T rich intergenic regions.Results have shown that in some rho mutants (DS502, Fll) mature tRNA was absent, but a few transcripts could be detected. Some high molecular weight species actually hybridized with DNA probes carrying different tRNA coding sequences. Low molecular weight transcripts (100-150 nucleotides, carrying one tRNA sequence) were also present in these mutants. A high molecular weight transcript was also observed in the wild type, though in much more 1i mited amount. The low molecular weight transcripts were analysed by the Sl mapping technique and found to include both a tRNA sequence and the upstream 5' flanking region extending as far as the 3' end of the preceding tRNA gene.The results suggest the existence of a common transcript bearing sever al tRNA sequences and indicate a possible mechanism of processing, which might be defective in mutants.

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Section: Discussionmentioning

confidence: 99%

Transcripts of mitochondrial tRNA genes inSaccharomyces cerevisiae

1982

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“…The existence of upstream transcription initiation sites, recognized by either polymerase II or III (23), could allow the formation of mRNA species which include the promoter sequences of structural genes, and which could be processed, polyadenylated, and reverse transcribed to give rise to new genes which contain transcription units with their 5' regulatory elements preserved (see review on pseudogenes in Vanin et al). Pseudogene MT-1i+b is an example of such a new gene.…”

Section: Methodsmentioning

confidence: 99%

Rat metallothionein-1 structural gene and three pseudogenes, one of which contains 5'-regulatory sequences.

Andersen¹,

Birren²,

Taplitz³

et al. 1986

Mol. Cell. Biol.

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As shown by Southern blot analysis, the metallothionein-1 (MT-1) genes in rats comprise a multigene family. We present the sequence of the MT-1 structural gene and compare its features with other metaliothionein genes. Three MT-1 pseudogenes which we sequenced apparently arose by reverse transcription of processed mRNA transcripts. Two of these, MT-1*a and MT-l*c, are retrogenes which derive from the MT-1 mRNA, having diverged from the MT-1 gene 6.9 and 2.6 million years ago, respectively. The third, MT-l*b, differs from the MT-1 cDNA by only three nucleotide alterations. Surprisingly, MT-l*b also preserves sequence homology for 142 base pairs 5' to the transcription initiation site of the parent gene; it contains a promoter sequence sufficient for specifying metal ion induction. We identified, by Si nuclease mapping, an RNA polymerase II initiation site 432 base pairs 5' of the MT-1 transcription initiation site of the MT-1 structural gene which could explain the formation of the mRNA precursor to this pseudogene. We were unable to detect MT-i*b transcripts, either in liver tissue or after transfection. We conclude that the absence of detectable transcripts from this pseudogene is due to either a reduced level of transcription or the formation of unstable transcripts as a consequence of the lack of a consensus sequence normally found 3' of transcription termination in the MT-1 structural gene.Metallothioneins are 6,000-dalton, cysteine-rich proteins that bind the metal ions zinc, copper, cadmium, and mercury (see 32 for review). Metallothioneins are usually isolated as two major isoforms, designated MT-1 and MT-2. The metallothionein (MT) genes are inducible by metal ions (4, 17), glucocorticoid hormones (19,20,36,37), stress (51), bacterial endotoxin (16), iodoacetate (18), and interferon (22). Human MT-1 and MT-2 genes show differential expression with metal ion and hormone inducers (57). The proposed functional roles of metallothioneins include: protection against heavy metal ion intoxication by cadmium or mercury (49); biological response to stress (51,64), and regulation of zinc and copper during development (3,5,52,59). The existence of numerous independent induction responses to different agents regulating MT gene expression suggests a complex role for the regulatory recognition sequences in these genes (16,22,30,43). The sequencing of members of a family of MT genes allowed us both to explore in detail the evolutionary relationship among these genes and to compare the regions of sequence involved in regulating MT gene expression. MATERIALS AND METHODSScreening of Charon 4a library, DNA sequence analysis, and computer analysis of sequence data. The screening of a rat liver Charon 4a genomic library for MT-1 sequences and the restriction maps for the inserts in p34 (MT-1 structural gene), p21 (MT-ltja), p27 (MT-lhb), and p5 (MT-14c) have already been reported (2). The sequence analysis of these clones was done by a combination of base-specific chemical cleavage of 5' end-labeled restriction fragments from...

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“…In cases where transcription products were to be used for a Northern analysis (see below), both the radioactive GTP precursor and the 5S RNA gene clone were omitted from the injection samples. Typically, [8][9][10] oocytes were injected with a given DNA solution. Following incubation (5-10 hours), the oocytes were frozen in liquid nitrogen and stored at -800 C until processed.…”

Section: Oocyte Injectionsmentioning

confidence: 99%

“…Two separate sets of intragenic sequences are required for Pol III transcription of tRNA genes. The first sequence (designated as the A block (10)) corresponds to a portion of the gene that codes for part of the D arm of the mature tRNA. The second sequence (the B block) spans the region of the gene where the TT1C stem-loop of the tRNA is encoded (10).…”

Section: Introductionmentioning

confidence: 99%