A quantity control mechanism regulating levels of the HapE subunit of the Hap complex in Aspergillus nidulans: HapC adjusts the number of HapE.
The CCAAT sequence is one of the most common cis-elements present in the promoter regions in eukaryotes. Aspergillus nidulans CCAAT-binding complex (Hap complex) consists of at least three subunits, HapB, HapC and HapE. To investigate the quantity control mechanisms of the subunits during assembly of the Hap complex, reconstitution studies with the recombinant subunits and the extracts prepared from the respective hap subunit deletion mutants were carried out. Furthermore, Western blot analysis on the Hap subunits and Northern blot analysis on the hap genes with the respective deletion mutants were also performed. From all the results together, it was suggested that the number of the HapC molecule could adjust that of the HapE molecule by forming stable heterodimers prior to assembly of the Hap complex. Although many CCAAT complexes have been characterized from various eukaryotes, little is known about stability of their subunits. The findings reported here suggest that similar quantity control mechanisms of the subunits may exist in the other eukaryotes. 1) M. Kato et al. FEBS Letters 512, 227-229 (2002).
Fungal Genet. Newsl. 50 (Supl):abstract
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22nd Fungal Genetics Conference