A conserved domain of yeast RNA triphosphatase flanking the catalytic core regulates self-association and interaction with the guanylyltransferase component of the mRNA capping apparatus Journal Article
| Authors: | Lehman, K.; Schwer, B.; Ho, C. K.; Rouzankina, I.; Shuman, S. |
| Article Title: | A conserved domain of yeast RNA triphosphatase flanking the catalytic core regulates self-association and interaction with the guanylyltransferase component of the mRNA capping apparatus |
| Abstract: | The 549-amino acid yeast RNA triphosphatase Cet1p catalyzes the first step in mRNA cap formation. Cet1p consists of three domains as follows: (i) a 230-amino acid N-terminal segment that is dispensable for catalysis in vitro and for Cet1p function in vivo; (ii) a protease-sensitive segment from residues 230 to 275 that is dispensable for catalysis but essential for Cet1p function in vivo; and (iii) a catalytic domain from residues 275 to 539. Sedimentation analysis indicates that purified Cet1(231-549)p is a homodimer. Cet1(231-549)p binds in vitro to the yeast RNA guanylyltransferase Ceg1p to form a 7.1 S complex that we surmise to be a trimer consisting of two molecules of Cet1(231-549)p and one molecule of Ceg1p. The more extensively truncated protein Cet1(276-549)p, which cannot support cell growth, sediments as a monomer and does not interact with Ceg1p. An intermediate deletion protein Cet1(246549)p, which supports cell growth only when overexpressed, sediments principally as a discrete salt-stable 11.5 S homo-oligomeric complex. These data implicate the segment of Ceg1p from residues 230 to 275 in regulating self-association and in binding to Ceg1p. Genetic data support the existence of a Ceg1p-binding domain flanking the catalytic domain of Cet1p, to wit: (i) the ts growth phenotype of 2μ CET1(246-549) is suppressed by overexpression of Ceg1p; (ii) a ts alanine cluster mutation CET1(201- 549)IK250A-W251A is suppressed by overexpression of Ceg1p; and (iii) 15 other cet-ts alleles with missense changes mapping elsewhere in the protein are not suppressed by Ceg1p overexpression. Finally, we show that the in vivo function of Cet1(275-549)p is completely restored by fusion to the guanylyltransferase domain of the mouse capping enzyme. We hypothesize that the need for Ceg1p binding by yeast RNA triphosphatase can by bypassed when the triphosphatase catalytic domain is delivered to the RNA polymerase II elongation complex by linkage in cis to the mammalian guanylyltransferase. |
| Keywords: | unclassified drug; mutation; sequence deletion; nonhuman; protein conformation; protein domain; mammalia; animals; mice; gene overexpression; cell growth; phosphatase; protein binding; rna triphosphatase; acid anhydride hydrolases; enzyme regulation; amino acid sequence; conserved sequence; molecular sequence data; messenger rna; saccharomyces cerevisiae; rna caps; dimerization; binding sites; molecular interaction; yeast; saccharomycetales; catalysis; catalytic domain; rna polymerase ii; candida albicans; nucleotidyltransferases; guanylyltransferase; suppression, genetic; priority journal; article; capping phenomenon; sedimentation rate |
| Journal Title: | Journal of Biological Chemistry |
| Volume: | 274 |
| Issue: | 32 |
| ISSN: | 0021-9258 |
| Publisher: | American Society for Biochemistry and Molecular Biology |
| Date Published: | 1999-08-06 |
| Start Page: | 22668 |
| End Page: | 22678 |
| Language: | English |
| DOI: | 10.1074/jbc.274.32.22668 |
| PUBMED: | 10428848 |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | Article -- Export Date: 16 August 2016 -- Source: Scopus |
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