N-terminal domain
of yeast eRF3 chain release factor is a negative cis-regulator of C-domain
function.
Kirill Osipov (1),
Kirill Volkov (1), Igor Valouev (2), Ludmila Mironova (1)
(1) Department of Genetics, St. Petersburg State University, Universitetskaya
nab, St. Petersburg, 199034, Russia (kvom@mail.ru); (2) Institute of
Experimental Cardiology, Cardiology Research Center, 3rd Cherepkovskaya Street,
Moscow, 121552, Russia
The product of yeast SUP35 gene, eRF3 chain release factor consists of three domains, N, M and C, of which only C domain is essential for termination and viability. The non-essential N domain is responsible for eRF3 prionization reducing termination efficiency and enhancing nonsense codons readthrough. Thus, the eRF3 N domain may be considered as a negative modulator of termination efficiency. Our data indicate that negative regulation of C domain functions by N domain can take place in the absence of prion form of eRF3 as well. This effect could be observed in some sup35 mutants containing amino acid replacements in the C domain. Nonsense suppression efficiency in strains bearing the full-length alleles is significantly higher than in isogenic strains bearing sup35C alleles (encoding eRF3, which consists of C domain only). Thus, the level of suppression, caused by sup35 mutations, at least in mutants studied, is determined by cumulative effect of mutations and N domain. Interestingly, an increase of termination efficiency in sup35C mutants coincides with a roughly fourfold increase of eRF3 amount in these strains comparatively to strains containing SUP35C of wild type. The mechanism of such regulation of eRF3 amount remains to be established. Supported by RFBR 02-04-49699 and CRDF ST-012 grants.