Unusual genome organisation in Entamoeba histolytica leads to two overlapping transcripts.
We have isolated homologs of the mini chromosome maintenance (MCM) gene family from the parasitic protozoan Entamoeba histolytica. The full length genomic and cDNA clones for the Eh MCM3 gene have been characterised. The Eh MCM3 gene is much smaller than the Saccharomyces cerevisiae MCM3 gene and other eukaryotic homologs of the MCM3/P1 family. The predicted Eh Mcm3 protein was 597 amino acids long and showed 37 and 46% positional identity with the Sc Mcm3 and the mouse P1 homologs respectively. While proceeding along the chromosome from the Eh MCM3 gene, we have identified a homolog (Eh PAK) of the murine p21 activated kinase (Rn KPAK), or S. cerevisiae STE20. Eh PAK lies 126 bp upstream of the Eh MCM3 gene. The predicted Eh p21 activated kinase protein was 459 amino-acids long and showed 33% positional identity with the murine p21 activated kinase and its yeast homolog Ste20. Analysis of cDNA and genomic sequences shows that the 3' untranslated region (UTR) of the Eh PAK mRNA and the 5' UTR of the Eh MCM3 mRNA are transcribed from a common 40 bp genomic segment. This is the first report of an amoeba gene being physically linked to a second gene such that their transcripts are overlapping and there is no non-transcribed intergenic region between the two genes. Primer extension studies have confirmed that unlike most E. histolytica genes, which have short 5' UTRs, the Eh MCM3 mRNA has a 126 bp long 5' UTR and the Eh PAK mRNA has a 265 bp long 5' UTR.
Gangopadhyay
S S
SS
Department of Biochemistry, Bose Institute, Calcutta, India.
Ray
S S
SS
Sinha
P
P
Lohia
A
A
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D004268:DNA-Binding Proteins; D004748:Entamoeba histolytica / Q000235:genetics*; D019204:GTP-Binding Proteins / Q000235:genetics; D005807:Genes, Overlapping; D018503:Genome, Protozoan; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D051379:Mice; D064126:Minichromosome Maintenance Complex Component 3; D008969:Molecular Sequence Data; D005810:Multigene Family; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D015800:Protozoan Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D018797:Cell Cycle Proteins; D004275:DNA, Ribosomal; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; C513269:Mcm3 protein, mouse; D009687:Nuclear Proteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D017346:Protein Serine-Threonine Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae; D019204:GTP-Binding Proteins; D064126:Minichromosome Maintenance Complex Component 3