A Novel E2f-Like Protein Involved in Transcriptional Activation of Cyst Wall Protein Genes in Giardia Lamblia
Resource
JOURNAL OF BIOLOGICAL CHEMISTRY v.286 n.39 pp.34101-34120
Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Journal Volume
v.286
Journal Issue
n.39
Pages
34101-34120
Date Issued
2011
Date
2011
Author(s)
SU, LI-HSIN
PAN, YU-JIAO
HUANG, YU-CHANG
CHO, CHAO-CHENG
CHEN, CHIA-WEI
SUN, CHIN-HUNG
Abstract
Giardia lamblia differentiates into resistant walled cysts for survival outside the host and transmission. During encystation, synthesis of cyst wall proteins is coordinately induced. The E2F family of transcription factors in higher eukaryotes is involved in cell cycle progression and cell differentiation. We asked whether Giardia has E2F-like genes and whether they influence gene expression during Giardia encystation. Blast searches of the Giardia genome database identified one gene (e2f1) encoding a putative E2F protein with two putative DNA-binding domains. We found that the e2f 1 gene expression levels increased significantly during encystation. Epitope-tagged E2F1 was found to localize to nuclei. Recombinant E2F1 specifically bound to the thymidine kinase and cwp1-3 gene promoters. E2F1 contains several key residues for DNA binding, and mutation analysis revealed that its binding sequence is similar to those of the known E 2F family proteins. The E2F1-binding sequences were positive cis-acting elements of the thymidine kinase and cwp 1 promoters. We also found that E2F1 transactivated the thymidine kinase and cwp1 promoters through its binding sequences in vivo. Interestingly, E2F1 overexpression resulted in a significant increase of the levels of CWP1 protein, cwp1-3 gene mRNA, and cyst formation. We also found E2F1 can interact with Myb2, a transcription factor that coordinate up-regulates the cwp1-3 genes during encystation. Our results suggest that E2F family has been conserved during evolution and that E2F1 is an important transcription factor in regulation of the Giardia cwp genes, which are key to Giardia differentiation into cysts.
Subjects
Differentiation
DNA-binding Protein
E2F Transcription Factor
Transcription
Transcription Factors
Transcription Regulation
Giardia
Cyst