title: Identification of EhTIF-IA: The putative E. histolytica orthologue of the human ribosomal RNA transcription initiation factor-IA.
abstract: Initiation of rDNA transcription requires the assembly of a specific multi-protein complex at the rDNA promoter containing the RNA Pol I with auxiliary factors. One of these factors is known as Rrn3P in yeast and Transcription Initiation Factor IA (TIF-IA) in mammals. Rrn3p/TIF-IA serves as a bridge between RNA Pol I and the pre-initiation complex at the promoter. It is phosphorylated at multiple sites and is involved in regulation of rDNA transcription in a growth-dependent manner. In the early branching parasitic protist Entamoeba histolytica, the rRNA genes are present exclusively on circular extra chromosomal plasmids. The protein factors involved in regulation of rDNA transcription in E. histolytica are not known. We have identified the E. histolytica equivalent of TIF-1A (EhTIF-IA) by homology search within the database and was further cloned and expressed. Immuno-localization studies showed that EhTIF-IA co-localized partially with fibrillarin in the peripherally localized nucleolus. EhTIF-IA was shown to interact with the RNA Pol I-specific subunit RPA12 both in vivo and in vitro. Mass spectroscopy data identified RNA Pol I-specific subunits and other nucleolar proteins to be the interacting partners of EhTIF-IA. Our study demonstrates for the first time a conserved putative RNA Pol I transcription factor TIF-IA in E. histolytica.
authors.affiliation: School of Environmental Sciences, Jawaharlal Nehru University, New Mehrauli Road, New Delhi 110 067, India.
authors.forename: Ankita
authors.initials: A
authors.lastname: Srivastava
authors.forename: Alok
authors.initials: A
authors.lastname: Bhattacharya
authors.forename: Sudha
authors.initials: S
authors.lastname: Bhattacharya
authors.forename: Gagan Deep
authors.initials: GD
authors.lastname: Jhingan
mesh_terms: D004275:DNA, Ribosomal / Q000235:genetics; D004748:Entamoeba histolytica / Q000235:genetics*; D006801:Humans; D009697:Nucleolus Organizer Region / Q000235:genetics; D035463:Pol1 Transcription Initiation Complex Proteins / Q000235:genetics* / Q000302:isolation & purification; D011401:Promoter Regions, Genetic; D012318:RNA Polymerase I / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
chemical_list: D004275:DNA, Ribosomal; D035463:Pol1 Transcription Initiation Complex Proteins; C101161:RRN3 protein, S cerevisiae; C428423:RRN3 protein, human; D029701:Saccharomyces cerevisiae Proteins; D012318:RNA Polymerase I