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Mol. Cell. Biol., Dec 1997, 6982-6993, Vol 17, No. 12
L Fernandes, C Rodrigues-Pousada and K Struhl
Saccharomyces cerevisiae contains eight members of a novel and fungus-
specific family of bZIP proteins that is defined by four atypical residues
on the DNA-binding surface. Two of these proteins, Yap1 and Yap2, are
transcriptional activators involved in pleiotropic drug resistance.
Although initially described as AP-1 factors, at least four Yap proteins
bind most efficiently to TTACTAA, a sequence that differs at position +/-2
from the optimal AP-1 site (TGACTCA); further, a Yap- like derivative of
the AP-1 factor Gcn4 (A239Q S242F) binds efficiently to the Yap recognition
sequence. Molecular modeling suggests that the Yap-specific residues make
novel contacts and cause physical constraints at the +/-2 position that may
account for the distinct DNA- binding specificities of Yap and AP-1
proteins. To various extents, Yap1, Yap2, Yap3, and Yap5 activate
transcription from a promoter containing a Yap recognition site.
Yap-dependent transcription is abolished in strains containing high levels
of protein kinase A; in contrast, Gcn4 transcriptional activity is
stimulated by protein kinase A. Interestingly, Yap1 transcriptional
activity is stimulated by hydrogen peroxide, whereas Yap2 activity is
stimulated by aminotriazole and cadmium. In addition, unlike other yap
mutations tested, yap4 (cin5) mutations affect chromosome stability, and
they suppress the cold-sensitive phenotype of yap1 mutant strains. Thus,
members of the Yap family carry out overlapping but distinct biological
functions.
Copyright © 1997, American Society for Microbiology
Yap, a novel family of eight bZIP proteins in Saccharomyces cerevisiae with distinct biological functions
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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