Molecular and Cellular Biology, January 1999, p. 99-106, Vol. 19, No. 1
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Copyright © 1999, American Society for Microbiology. All rights reserved.

andDepartment of Genetics, University of Melbourne, Parkville, Victoria 3052, Australia,1 and Institut fuer Genetik und Mikrobiologie, Ludwig-Maximilians-Universität, Munich 80638, Germany2
Received 2 July 1998/Returned for modification 25 August 1998/Accepted 29 September 1998
CCAAT binding factors (CBFs) positively regulating the expression
of the amdS gene (encoding acetamidase) and two penicillin biosynthesis genes (ipnA and aatA) have been
previously found in Aspergillus nidulans. The factors were
called AnCF and PENR1, respectively. Deletion of the hapC
gene, encoding a protein with significant similarity to Hap3p of
Saccharomyces cerevisiae, eliminated both AnCF and PENR1
binding activities. We now report the isolation of the genes
hapB and hapE, which encode proteins with
central regions of high similarity to Hap2p and Hap5p of S. cerevisiae and to the CBF-B and CBF-C proteins of mammals. An
additional fungus-specific domain present in HapE was revealed by
comparisons with the homologs from S. cerevisiae,
Neurospora crassa, and Schizosaccharomyces pombe. The HapB, HapC, and HapE proteins have been shown to be necessary and sufficient for the formation of a CCAAT binding complex
in vitro. Strains with deletions of each of the hapB, hapC, and hapE genes have identical phenotypes
of slow growth, poor conidiation, and reduced expression of
amdS. Furthermore, induction of amdS by omega
amino acids, which is mediated by the AmdR pathway-specific activator,
is abolished in the hap deletion mutants, as is growth on
-aminobutyric acid as a sole nitrogen or carbon source. AmdR and
AnCF bind to overlapping sites in the promoters of the amdS
and gatA genes. It is known that AnCF can bind
independently of AmdR. We suggest that AnCF binding is required for
AmdR binding in vivo.
Present address: Institut für Mikrobiologie und Genetik,
Technische Universität Darmstadt, 64287 Darmstadt, Germany.
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