Functional analysis of the transcriptional activator XlnR from Aspergillus niger

Abstract

The transcriptional activator XlnR from Aspergillus niger is a zinc binuclear cluster transcription factor that belongs to the GAL4 superfamily. Several putative structural domains in XlnR were predicted using database and protein sequence analysis. Thus far, only the functionality of the N-terminal DNA-binding domain has been determined experimentally. Deletion mutants of the xlnR gene were constructed to localize the functional regions of the protein. The results showed that a putative C-terminal coiled-coil region is involved in nuclear import of XlnR. After deletion of the C-terminus, including the coiled-coil region, XlnR was found in the cytoplasm, while deletion of the C-terminus downstream of the coiled-coil region resulted in nuclear import of XlnR. The latter mutant also showed increased xylanase activity, indicating the presence of a region with an inhibitory function in XlnR-controlled transcription. Previous findings had already shown that a mutation in the XlnR C-terminal region resulted in transcription of the structural genes under non-inducing conditions. A regulatory model of XlnR is presented in which the C-terminus responds to repressing signals, resulting in an inactive state of the protein.

Deciphering Transcriptional Regulatory Mechanisms Associated with Hemicellulose Degradation in Neurospora crassa

“…Regulation of hemicellulase gene expression has focused on induction by different inducers and transcriptional regulation mediated by XYR1/XlnR (25,31,34,38,51,63,64; also reviewed in references 52 and 61). In Aspergillus and H. jecorina, xlnR/xyr1 is also regulated by carbon catabolite repression (CCR) (16,44,53,56).…”

Rapid shifts in Atta cephalotes fungus-garden enzyme activity after a change in fungal substrate (Attini, Formicidae)

“…For the samples of the debris pile, 6 ll of the supernatant was applied in the wells in duplicate. After 22 h of incubation at 25°C, the plates were photographed and the area of the blue halo surrounding each well [which is a quantitative measure for the amount of enzyme activity (Hasper et al, 2004;Schiøtt et al, 2008;Pedersen et al, 2009;] was measured using the software program ImageJ ver. 1.41 for Macintosh (Fig.…”

Xyr1 (Xylanase Regulator 1) Regulates both the Hydrolytic Enzyme System and d -Xylose Metabolism in Hypocrea jecorina

“…For the A. niger XlnR protein, the possible participation of Ace1 in transcriptional regulation of hydrolase-encoding genes has not yet been shown, and an Ace2 homologue could not even be found in the genome. In addition, it was suggested that XlnR binds as a monomer since it was shown to bind to a nonpalindromic consensus in the promoter (14,48). In contrast to Xyr1, XlnR seems to act as an unspecific transactivator of a wide variety of genes encoding hydrolytic enzymes responding mainly to Dxylose induction, largely independent of other substrate-specific regulatory proteins.…”