DNA topoisomerase IIIβ promotes cyst generation by inducing cyst wall protein gene expression in Giardia lamblia
Journal
Open Biology
Journal Volume
10
Journal Volume
10
Journal Issue
2
Journal Issue
2
Pages
190228
Start Page
article 190228
Date Issued
2020
Author(s)
Abstract
Giardia lamblia causes waterborne diarrhoea by transmission of infective cysts. Three cyst wall proteins are highly expressed in a concerted manner during encystation of trophozoites into cysts. However, their gene regulatory mechanism is still largely unknown. DNA topoisomerases control topological homeostasis of genomic DNA during replication, transcription and chromosome segregation. They are involved in a variety of cellular processes including cell cycle, cell proliferation and differentiation, so they may be valuable drug targets. Giardia lamblia possesses a type IA DNA topoisomerase (TOP3β) with similarity to the mammalian topoisomerase IIIβ. We found that TOP3β was upregulated during encystation and it possessed DNA-binding and cleavage activity. TOP3β can bind to the cwp promoters in vivo using norfloxacin-mediated topoisomerase immunoprecipitation assays. We also found TOP3β can interact with MYB2, a transcription factor involved in the coordinate expression of cwp1-3 genes during encystation. Interestingly, overexpression of TOP3β increased expression of cwp1-3 and myb2 genes and cyst formation. Microarray analysis confirmed upregulation of cwp1-3 and myb2 genes by TOP3β. Mutation of the catalytically important Tyr residue, deletion of C-terminal zinc ribbon domain or further deletion of partial catalytic core domain reduced the levels of cleavage activity, cwp1-3 and myb2 gene expression, and cyst formation. Interestingly, some of these mutant proteins were mis-localized to cytoplasm. Using a CRISPR/Cas9 system for targeted disruption of top3β gene, we found a significant decrease in cwp1-3 and myb2 gene expression and cyst number. Our results suggest that TOP3β may be functionally conserved, and involved in inducing Giardia cyst formation. ? 2020 The Authors.
Subjects
Cyst; Differentiation; DNA-binding protein; Giardia; Topoisomerase IIIβ; Transcription
Other Subjects
DNA topoisomerase; Myb2 protein, Giardia lamblia; protozoal protein; transactivator protein; cell wall; chemistry; DNA microarray; enzyme active site; enzymology; gene expression profiling; gene expression regulation; genetics; Giardia intestinalis; metabolism; mutation; physiology; procedures; promoter region; upregulation; Catalytic Domain; Cell Wall; DNA Topoisomerases, Type I; Gene Expression Profiling; Gene Expression Regulation; Giardia lamblia; Mutation; Oligonucleotide Array Sequence Analysis; Promoter Regions, Genetic; Protozoan Proteins; Trans-Activators; Up-Regulation
Publisher
Royal Society Publishing
Type
journal article