Multifarious Transcriptional Regulation of Adhesion Protein Gene Ap65-1 by a Novel Myb1 Protein in the Protozoan Parasite Trichomonas Vaginalis
Resource
EUKARYOTIC CELL v.5 n.2 pp.391-399
Journal
EUKARYOTIC CELL
Journal Volume
v.5
Journal Issue
n.2
Pages
391-399
Date Issued
2006
Date
2006
Author(s)
ONG, SHIOU-JENG
HSU, HONG-MING
LIU, HSING-WEI
TAI, JUNG-HSIANG
Abstract
Transcription efficiency of an adhesion protein gene, ap65-1 , in Trichomonas vaginalis varies with changes in the iron supply and growth stages. In the present study, two Myb recognition elements, MRE-1/MRE-2r and MRE-2f, were found to play antagonistic roles in regulating iron- inducible activity of an ap65-1 reporter gene. Intriguingly, either of these elements was shown to be sufficient to repress basal activity, but together they were also shown to activate growth-related activity, of the reporter gene in iron- depleted cells. A myb1 gene, which encodes a 24-kDa open reading frame containing a Myb-like R2R3 DNA binding domain, was identified from Southwestern screening of MRE-2f- binding proteins. The Myb1 protein was detected as a major 35-kDa protein, which exhibited variations in nuclear concentrations with changes in the iron supply. A recombinant Myb1 was shown to differentially interact with MRE-1/MRE-2r and MRE-2f in vitro. Overexpression of a hemagglutinin-tagged Myb1 in T. vaginalis resulted in repression or activation of ap65-1 transcription in iron- depleted cells at an early or a late stage of cell growth, respectively, while iron-inducible ap65-1 transcription was constitutively repressed. The hemagglutinin-tagged Myb1 was found to constantly occupy the chromosomal ap65-1 promoter at a proximal site, but it also selected two more distal sites only at the late growth stage. Together, these observations suggest that Myb1 critically regulates multifarious ap65-1 transcription, possibly via differential selection of multiple promoter sites upon environmental changes.
Subjects
INITIATOR-BINDING-PROTEIN
DNA-BINDING
PRIMITIVE EUKARYOTE
MOLECULAR CHARACTERIZATION
PROMOTER RECOGNITION
CORE PROMOTER