A characterization of mRNA activities and their sequence complexities in Trypanosoma brucei: partial purification and properties of the VSSA mRNA

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Abstract
Polyadenylated RNA isolated from a clone of Trypanosoma brucei was shown to direct the synthesis of a variety of polypeptides in a cell-free system. A predominant 58,000 dalton polypeptide was immunoprecipitated with antisera to the T. brucei variant specific surface antigen (VSSA). The mRNA that directed the synthesis of the VSSA was 2.0 kilobases (kb) long as measured by polyacrylamide gel electrophoresis in 98% formamide. Complementary DNA was prepared with avian myeloblastosis virus reverse transcriptase and the nucleotide sequence complexities of the total polysomal poly(A)+RNA and a gel purified VSSA mRNA were measured. 20% of the total cellular poly(A)+RNA contained abundant sequences with an apparent complexity of 9.6 kb; 42% of the purified VSSA mRNA contained abundant sequences with a complexity of 7.2 kb. Complementary DNA synthesized from gel purified VSSA mRNA was hybridized to total cellular poly(A)+RNA isolated from an unrelated T. brucei clone expressing a different variant antigen. A portion of the low complexity RNA sequence component was absent in the heterologous mRNA population but the same plateau of hybridization was achieved (93%). The abundance of some of the low complexity mRNAs appears to be T. brucei clone specific.