RESUMO
RNAs were isolated from Entamoeba histolytica with a high salt sodium dodecylsulfate-diethylpyrocarbonate technique. Majority species of 25 S, 17 S and 4 S RNAs were detected after sucrose gradient centrifugation. An additional 5 S RNA was detected by polyacrylamide gel electrophoresis. The molecular weights of these RNAs as determined by completely denaturing polyacrylamide gel electrophoresis were 1.31 X 10(6) (25 S), 0.803 X 10(6) (17 S), 4.0 X 10(4) (5 S) and 2.5 X 10(4) (4 S). The 25 S RNA was labile and dissociated under mild denaturing conditions (between 37 degrees C and 55 degrees C) into 17 S and 16 S RNAs with molecular weights of 0.700 X 10(6) and 0.614 X 10(6), respectively; under completely denaturing conditions an additional 5.8 S RNA with a molecular weight of 4.8 X 10(4) was detected. Evidence is presented which suggests that the lability of the 25 S RNA is the result of an in vivo cleavage rather than one which is generated during RNA isolation.
