Nucleic Acids Research, Vol. 20, No. 20 5477
.) 1992 Oxford University Press
A cluster of tRNA genes is present in the 5'-flanking region of the chicken ubiquitin gene Ubil Jovita Mezquita and Cristobal Mezquita* Molecular Genetics Research Group, Faculty of Medicine, University of Barcelona, Casanova 143, 08036 Barcelona, Spain EMBL accession no. Z14958
Submitted September 14, 1992 Five new tRNA genes have been identified by sequencing the 5'-flanking region of the chicken polyubiquitin gene UbHI. Sequences coding for Ala-tRNA, Asp-tRNA, Phe-tRNA, AsptRNA and Ala-tRNA are present 1.9 kb upstream of the initiation site of the polyubiquitin UbII gene (Figure 1). Ubiquitin conjugation has a fundamental role in mediating intracellular selective protein degradation (1-3). Recognition of target proteins as substrates for ubiquitination depends on the identity of their N-terminal residues (N-end rule) (3). In addition, the ubiquitin-dependent degradation of some proteins was found to require tRNA (4). Aminoacyl tRNA-protein transferases, which conjugate specific amino acids to the N-termini of acceptor proteins, may provide a mechanism for selective degradation or stabilization of proteins during cell differentiation (3). Following multiubiquitination, the target protein is degraded by the 26S proteasome, a large ATP dependent multicatalytic proteinase that contains more than twenty distinct protein subunits and also molecules of tRNA (5). The observed relationship between tRNAs, multiubiquitination and selective proteolysis suggests that the close proximity between
the tRNA cluster and the polyubiquitin UbIH gene, a gene preferentially expressed in certain tissues (6), may be related with co-regulation of gene expression of tRNAs and ubiquitin. Coregulation could be important to assure the cell a proper ratio of tRNAs to ubiquitin for polyubiquitination of those target proteins which require a tRNA mediated addition of new Nterminal amino acids (3).
ACKNOWLEDGEMENT This research was supported by CICYT grant PM89-0051.
REFERENCES Hershko,A. (1991) Trends Biochem. Sci. 16, 265-268. Rechsteiner,M. (1991) Cell 66, 615-618. Varshavsky,A. (1992) Cell 69, 725-735. Ciechanover,A., Wolin,S.L., Steitz,A. and Lodish,H.F. (1985) Proc. Natl. Acad. Sci. USA 82, 1341-1345. 5. Nothwang,H.G., Coux,O., Keith,G. Silva-Pereira,I., Scherrer,K. (1992) Nucleic Acids Res. 20, 1959-1965. 6. Mezquita,J. and Mezquita,C. (1991) FEBS Len. 279, 69-72.
1. 2. 3. 4.
Ala Asp Phe ASp Ma,a 279bp-(1J11 2bP- -288bp1 l -183bp-[I -273bp- [-1883bptRNA tRNA tRNA tENA tRNA AAGCTTTGGTGTCGTAGAGCCGTGGTGCTCAGCACTMCCCCAGCAGCAGGGGTTGCAGCAGCACTTTGCAGCCTGTTTGGGAGGGGTGA AAAAAGCCAAGTGTGGTGCTGATTTACAAGTGACAAAGGTGAAATAGGGGTCTTTAGGGAATCTTGGCGAGTGAAACTAAGGTAGCATGG
90 180 CGTTGCAGAGAGCTTCTGCTTTCTGCCTGTGAATTGAGGGAGAGGGATAGAAAATAGAAAAAGCGGAGGAAAGAAAGAGAAGGGAAAGAA 270 AAAAAACTGTGGAGATGCCGGGGATTGAACCCGGGGCCTCATACATGCAAAGCATGCGCTCTACCACTGAGCTACATCCCCTTGCTGCGA 360 450 ATGGCTTTTGCAGAACGCCATCATCATATAGACGGCCGTCGCGCGCCACCAGCTGGGCTATGATGTTGTTGCAGAGTCGGAGGAAGAAAC TCGAAAGCACCTGTCCTCGTTAGTATAGTGGTGAGTATCCCCGCCTGTCACGCGGGAGACCGGGGTTCGATTCCCCGACGGGGAGAGAGA 540 GAACATTTTGACCGTCGGCGCAATTTTTTCTCCTGGAGGCCCCGACACTGGTGGCACGTAGGGCCGTGACGGGGGGGCAGTCACCGCGGG 630 GTAGCCGGCGGCCCATCTTTATTTCCCGGGCTTTAGCGCAGAGCGATGGGAGATACGGGGAGGCTCCCAGGCGACAGCGCCCCCGGAGCC 720 GCGCGCCGCCGCGAACGGACGTCCCCACGTGCTCGCGCTGCACGAAGCGCAGGGACAGGCGGGGGCTGGGCGGGGTCGTATTACAGCCCG 810 GGAAGGGTCGTCTC9CCGCCGAAATAGCTCAGTTGGGAGAGCGTTAGACTGAAGATCTAAGGTCCCTGGTTCGATCCCGGGTTTCGGCA900 GAGAAATCTTTTTTTCTTCATTGTTTCTCTAATTCTCCCCACGGCTGTCGCATTGCAGCCCAGCAGCTCGCGGTTCCCCCCGGCCGCAGG 990
GGTCGCGGCGCGGGGCGCTCCCGGCGGCAGTAACACGTAGCGCCCGCGTGGGGGCTGAGCTCGAGCGGCCCGCGGGAGCACTGCCCGTAG CTTCCTCGTTAGTATAGTGGTGAGTATCCCCGCCTGTCACGCGGGAGACCGGGGTTCGATTCCCCGACGGGGAGGTGATATATTTTTTTT
TCACTTCATGAAATTTTTCTCTCCTCACTTTTCTTCCCTTGAATTATTACGGCTCCCGAAGAGAAAAAAAAAAATCATACAGCCGTCCGT GCGCGCACACAGAGTGCTTCTGTACTCCAGGAGACACCCAAAGCGCACCGAGCGCAGCCCGCGCTGCTCCCCGCCCCGCCCGGCAGGCAG CTCCGCGGCGCGCTGTTCCCCACTCGGATGAATGAAGGACGGAGCGGTGGGGCCGGCGAGTGGGCAGCGCGGGCAGGGGGATGTAGCTC GCGGTAGAGCGCATGCTTTGCATGTATGAGGTCCCGGGTTCAATCCCCGGCATCTCCACGGGCGCCCAGTACTTTTGTCCACATTGCGCA
1080 1170 1260 1350 1440 1530
Figure 1. Sequence of the 5'-flanking region of the chicken polyubiquitin gene UbIl containing a cluster of tRNAs: Ala-tRNA (complementary strand), Asp-tRNA, Phe-tRNA, Asp-tRNA and Ala-tRNA. The tRNA's sequences are underlined.
*
To whom
correspondence
should be addressed
.) 1992 Oxford University Press
A cluster of tRNA genes is present in the 5'-flanking region of the chicken ubiquitin gene Ubil Jovita Mezquita and Cristobal Mezquita* Molecular Genetics Research Group, Faculty of Medicine, University of Barcelona, Casanova 143, 08036 Barcelona, Spain EMBL accession no. Z14958
Submitted September 14, 1992 Five new tRNA genes have been identified by sequencing the 5'-flanking region of the chicken polyubiquitin gene UbHI. Sequences coding for Ala-tRNA, Asp-tRNA, Phe-tRNA, AsptRNA and Ala-tRNA are present 1.9 kb upstream of the initiation site of the polyubiquitin UbII gene (Figure 1). Ubiquitin conjugation has a fundamental role in mediating intracellular selective protein degradation (1-3). Recognition of target proteins as substrates for ubiquitination depends on the identity of their N-terminal residues (N-end rule) (3). In addition, the ubiquitin-dependent degradation of some proteins was found to require tRNA (4). Aminoacyl tRNA-protein transferases, which conjugate specific amino acids to the N-termini of acceptor proteins, may provide a mechanism for selective degradation or stabilization of proteins during cell differentiation (3). Following multiubiquitination, the target protein is degraded by the 26S proteasome, a large ATP dependent multicatalytic proteinase that contains more than twenty distinct protein subunits and also molecules of tRNA (5). The observed relationship between tRNAs, multiubiquitination and selective proteolysis suggests that the close proximity between
the tRNA cluster and the polyubiquitin UbIH gene, a gene preferentially expressed in certain tissues (6), may be related with co-regulation of gene expression of tRNAs and ubiquitin. Coregulation could be important to assure the cell a proper ratio of tRNAs to ubiquitin for polyubiquitination of those target proteins which require a tRNA mediated addition of new Nterminal amino acids (3).
ACKNOWLEDGEMENT This research was supported by CICYT grant PM89-0051.
REFERENCES Hershko,A. (1991) Trends Biochem. Sci. 16, 265-268. Rechsteiner,M. (1991) Cell 66, 615-618. Varshavsky,A. (1992) Cell 69, 725-735. Ciechanover,A., Wolin,S.L., Steitz,A. and Lodish,H.F. (1985) Proc. Natl. Acad. Sci. USA 82, 1341-1345. 5. Nothwang,H.G., Coux,O., Keith,G. Silva-Pereira,I., Scherrer,K. (1992) Nucleic Acids Res. 20, 1959-1965. 6. Mezquita,J. and Mezquita,C. (1991) FEBS Len. 279, 69-72.
1. 2. 3. 4.
Ala Asp Phe ASp Ma,a 279bp-(1J11 2bP- -288bp1 l -183bp-[I -273bp- [-1883bptRNA tRNA tRNA tENA tRNA AAGCTTTGGTGTCGTAGAGCCGTGGTGCTCAGCACTMCCCCAGCAGCAGGGGTTGCAGCAGCACTTTGCAGCCTGTTTGGGAGGGGTGA AAAAAGCCAAGTGTGGTGCTGATTTACAAGTGACAAAGGTGAAATAGGGGTCTTTAGGGAATCTTGGCGAGTGAAACTAAGGTAGCATGG
90 180 CGTTGCAGAGAGCTTCTGCTTTCTGCCTGTGAATTGAGGGAGAGGGATAGAAAATAGAAAAAGCGGAGGAAAGAAAGAGAAGGGAAAGAA 270 AAAAAACTGTGGAGATGCCGGGGATTGAACCCGGGGCCTCATACATGCAAAGCATGCGCTCTACCACTGAGCTACATCCCCTTGCTGCGA 360 450 ATGGCTTTTGCAGAACGCCATCATCATATAGACGGCCGTCGCGCGCCACCAGCTGGGCTATGATGTTGTTGCAGAGTCGGAGGAAGAAAC TCGAAAGCACCTGTCCTCGTTAGTATAGTGGTGAGTATCCCCGCCTGTCACGCGGGAGACCGGGGTTCGATTCCCCGACGGGGAGAGAGA 540 GAACATTTTGACCGTCGGCGCAATTTTTTCTCCTGGAGGCCCCGACACTGGTGGCACGTAGGGCCGTGACGGGGGGGCAGTCACCGCGGG 630 GTAGCCGGCGGCCCATCTTTATTTCCCGGGCTTTAGCGCAGAGCGATGGGAGATACGGGGAGGCTCCCAGGCGACAGCGCCCCCGGAGCC 720 GCGCGCCGCCGCGAACGGACGTCCCCACGTGCTCGCGCTGCACGAAGCGCAGGGACAGGCGGGGGCTGGGCGGGGTCGTATTACAGCCCG 810 GGAAGGGTCGTCTC9CCGCCGAAATAGCTCAGTTGGGAGAGCGTTAGACTGAAGATCTAAGGTCCCTGGTTCGATCCCGGGTTTCGGCA900 GAGAAATCTTTTTTTCTTCATTGTTTCTCTAATTCTCCCCACGGCTGTCGCATTGCAGCCCAGCAGCTCGCGGTTCCCCCCGGCCGCAGG 990
GGTCGCGGCGCGGGGCGCTCCCGGCGGCAGTAACACGTAGCGCCCGCGTGGGGGCTGAGCTCGAGCGGCCCGCGGGAGCACTGCCCGTAG CTTCCTCGTTAGTATAGTGGTGAGTATCCCCGCCTGTCACGCGGGAGACCGGGGTTCGATTCCCCGACGGGGAGGTGATATATTTTTTTT
TCACTTCATGAAATTTTTCTCTCCTCACTTTTCTTCCCTTGAATTATTACGGCTCCCGAAGAGAAAAAAAAAAATCATACAGCCGTCCGT GCGCGCACACAGAGTGCTTCTGTACTCCAGGAGACACCCAAAGCGCACCGAGCGCAGCCCGCGCTGCTCCCCGCCCCGCCCGGCAGGCAG CTCCGCGGCGCGCTGTTCCCCACTCGGATGAATGAAGGACGGAGCGGTGGGGCCGGCGAGTGGGCAGCGCGGGCAGGGGGATGTAGCTC GCGGTAGAGCGCATGCTTTGCATGTATGAGGTCCCGGGTTCAATCCCCGGCATCTCCACGGGCGCCCAGTACTTTTGTCCACATTGCGCA
1080 1170 1260 1350 1440 1530
Figure 1. Sequence of the 5'-flanking region of the chicken polyubiquitin gene UbIl containing a cluster of tRNAs: Ala-tRNA (complementary strand), Asp-tRNA, Phe-tRNA, Asp-tRNA and Ala-tRNA. The tRNA's sequences are underlined.
*
To whom
correspondence
should be addressed
