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Refining the pH response in A spergillus nidulans : a modulatory triad involving PacX , a novel zinc binuclear cluster protein
Author(s) -
Bussink HenkJan,
Bignell Elaine M.,
MúneraHuertas Tatiana,
LucenaAgell Daniel,
Scazzocchio Claudio,
Espeso Eduardo A.,
Bertuzzi Margherita,
Rudnicka Joanna,
NegreteUrtasun Susana,
PeñasParilla Maria M.,
Rainbow Lynne,
Peñalva Miguel Á.,
Arst Herbert N.,
Tilburn Joan
Publication year - 2015
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.13173
Subject(s) - aspergillus nidulans , biology , transposable element , mutagenesis , transcription factor , psychological repression , derepression , zinc finger , transposon mutagenesis , proteolysis , microbiology and biotechnology , biochemistry , mutation , gene , mutant , gene expression , enzyme
Summary The A spergillus nidulans PacC transcription factor mediates gene regulation in response to alkaline ambient pH which, signalled by the P al pathway, results in the processing of PacC 72 to PacC 27 via PacC 53 . Here we investigate two levels at which the pH regulatory system is transcriptionally moderated by pH and identify and characterise a new component of the pH regulatory machinery, PacX . Transcript level analysis and overexpression studies demonstrate that repression of acid‐expressed pal F , specifying the Pal pathway arrestin, probably by PacC 27 and/or PacC 53 , prevents an escalating alkaline pH response. Transcript analyses using a reporter and constitutively expressed pac C trans ‐alleles show that pac C preferential alkaline‐expression results from derepression by depletion of the acid‐prevalent PacC 72 form. We additionally show that pac C repression requires PacX . pac X mutations suppress PacC processing recalcitrant mutations, in part, through derepressed PacC levels resulting in traces of PacC 27 formed by pH ‐independent proteolysis. pac X was cloned by impala transposon mutagenesis. PacX , with homologues within the L eotiomyceta, has an unusual structure with an amino‐terminal coiled‐coil and a carboxy‐terminal zinc binuclear cluster. pacX mutations indicate the importance of these regions. One mutation, an unprecedented finding in A . nidulans genetics, resulted from an insertion of an endogenous F ot1 ‐like transposon.