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A second Zn(II) 2 Cys 6 transcriptional factor encoded by the YNA2 gene is indispensable for the transcriptional activation of the genes involved in nitrate assimilation in the yeast Hansenula polymorpha
Author(s) -
Ávila Julio,
González Celedonio,
Brito Nélida,
Machín, M Félix,
Pérez Dolores,
Siverio José M.
Publication year - 2002
Publication title -
yeast
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.923
H-Index - 102
eISSN - 1097-0061
pISSN - 0749-503X
DOI - 10.1002/yea.847
Subject(s) - nitrogen assimilation , biology , nitrate reductase , nitrate , gene , biochemistry , mutant , nitrite reductase , gene expression , promoter , gene cluster , microbiology and biotechnology , enzyme , ecology
Nitrate assimilation genes encoding a nitrate transporter ( YNT1 ), nitrite reductase ( YNI1 ), a Zn(II) 2 Cys 6 transcriptional factor involved in nitrate induction ( YNA1 ) and the nitrate reductase ( YNR1 ) are clustered in the yeast Hansenula polymorpha . A second gene, termed YNA2 (yeast nitrate assimilation), was located seven nucleotides away from the 3′ region of YNR1 gene. The cluster is flanked by an ORF encoding a protein with similarity to glutathione‐ S ‐transferase on the YNT1 side and an ORF with similarity to Saccharomyces cerevisiae Rad3p on the YNA2 side. The disruption of YNA2 confers the resulting null mutant strain with inability to grow in nitrate. The YNA2 gene encodes a putative protein of 618 residues bearing in the N‐terminus the consensus sequence Cys–X 2 –Cys–X 6 –Cys–X 5–16 –Cys–X 2 –Cys–X 6–8 –Cys characteristic of the Zn(II) 2 Cys 6 transcriptional factors. YNA2 is therefore a member of the H. polymorpha nitrate assimilation gene cluster which is transcribed in the opposite direction to the rest of the members. Yna2p shares about 27% similarity with the H. polymorpha Yna1p Zn(II) 2 Cys 6 transcriptional factor involved in nitrate induction. Unlike the wild‐type, the yna2::URA3 strain showed no expression of the nitrate assimilation genes when incubated in nitrate for 2 h. With regard to YNA2 expression, similar YNA2 transcript levels were observed in ammonium and in ammonium plus nitrate, but about a four‐fold higher expression was observed in nitrate. However, this induction by nitrate of the YNA2 gene was not observed in the Δyna1::URA3 strain. On the contrary, the pattern of YNA1 expression was the same in the wild‐type as in the yna2::URA3 strain, indicating that YNA2 does not affect YNA1 expression. The nucleotide sequence Accession No. for YNA2 is AJ223294. Copyright © 2002 John Wiley & Sons, Ltd.