Sequence heterogeneity in the Spliced Leader RNA gene promoter in Trypanosoma cruzi CL-Brener. A molecular trace of the hybrid origin of this strain?

CRIBB PAMELA; TAPIA ELIZABETH; DIOSQUE PATRICIO; SERRA ESTEBAN

Rosario, Argentina

Congreso; XX Reunión Anual de la Sociedad Argentina de Protozoología; 2004

Sociedad Argentina de Protozoología

Sequence heterogeneity in the Spliced Leader RNA gene promoter in Trypanosoma cruzi CL-Brener. A molecular trace of the hybrid origin of this strain? Pamela Cribb, Elizabeth Tapia#, Patricio Diosque§ y Esteban Serra. IBR- Fac. Cs. Bioq. y Farm. UNR. #Fac. Cs. Exactas, Ing. y Agrim. UNR. §Lab. Patología Experimental, Fac. Cs. de la Salud, UNSalta.  pcribb@fbioyf.unr.edu.ar Spliced Leader (SL) RNAs from trypanosomatids are encoded in highly repetitive genes, independently transcribed from their own promoters. Both gene and promoter sequences vary between species. Trypanosoma cruzi is divided into two phylogenetic lineages, T. cruzi I and T. cruzi II, which contain different SL RNA gene promoter sequences. Class I SL gene promoter sequences, found in T. cruzi II are highly conserved in the –80/+1 region, whereas Class II promoters from T. cruzi I are more variable. We cloned and sequenced different SL RNA promoter sequences from CL-Brener reference strain, belonging to T. cruzi II lineage. Surprisingly, we detected a sequence that differed within the –80/+1 region with the sequence previously reported for this strain. In order to further analyze the heterogeneity in the promoter region of CL-Brener strain, 1700 SL promoter sequences were obtained from  973418 T. cruzi genome project single pass sequences. A detailed analysis of these promoters discovered new divergent CL-Brener sequences with typical T. cruzi I features, showing T. cruzi I/T. cruzi II hybrid characteristics. Ten of these sequences were selected to be analyzed with Mr. Bayes program together with promoter sequences from both lineages. The program classified the data in two clades, grouping all T. cruzi II together with 8 of the new sequences in one, and T.cruzi I and 2 new ones in the other. The results presented herein show that sequence heterogeneity in SL RNA gene promoter not only exists between T. cruzi strains but also within CL-Brener strain. These CL-Brener “T. cruzi I-like” sequences could be considered a molecular trace of a hybrid origin of the SL RNA gene and a new evidence for the presence of sequences of T. cruzi I origin into a T. cruzi II strain. The results presented herein show that sequence heterogeneity in SL RNA gene promoter not only exists between T. cruzi strains but also within CL-Brener strain. These CL-Brener “T. cruzi I-like” sequences could be considered a molecular trace of a hybrid origin of the SL RNA gene and a new evidence for the presence of sequences of T. cruzi I origin into a T. cruzi II strain. The results presented herein show that sequence heterogeneity in SL RNA gene promoter not only exists between T. cruzi strains but also within CL-Brener strain. These CL-Brener “T. cruzi I-like” sequences could be considered a molecular trace of a hybrid origin of the SL RNA gene and a new evidence for the presence of sequences of T. cruzi I origin into a T. cruzi II strain. The results presented herein show that sequence heterogeneity in SL RNA gene promoter not only exists between T. cruzi strains but also within CL-Brener strain. These CL-Brener “T. cruzi I-like” sequences could be considered a molecular trace of a hybrid origin of the SL RNA gene and a new evidence for the presence of sequences of T. cruzi I origin into a T. cruzi II strain.