FIG. 4.

hU3-55k is a specific U3 snoRNP component. (A) 55k-VSV, 55k, and pCI-neo were transiently expressed in HeLa cells. Two days after transfection, cells were lysed and used for immunoprecipitation with anti-VSV (αVSV), antifibrillarin (αFibrillarin), and anti-U2B" (αU2B") antibodies. RNAs were extracted from immunoprecipitates (lanes 2 through 10) and total cell extracts (lanes 1, 11, and 12), resolved by PAGE, and transferred to a Northern blot. Specific antisense RNA probes were used to detect human U3, U8, and U2 sn(o)RNAs, as indicated on the right. Lanes 2 through 4, anti-VSV immunoprecipitations; lanes 5 through 7, antifibrillarin immunoprecipitations; lanes 8 through 10, anti-U2B" immunoprecipitations; lanes 1, 11, and 12, RNA isolated from 5% of indicated total cell extracts used for immunoprecipitations. (B) 55k-VSV and 55k were transiently expressed in HeLa cells. Two days after transfection, cells were lysed and used for immunoprecipitation with anti-VSV and antifibrillarin (αFib) antibodies. RNAs were extracted from immunoprecipitates and total cell extracts, 3′ end labeled with [³²P]pCp, and resolved on an 8% denaturing polyacrylamide gel. Lanes 3 through 4, anti-VSV immunoprecipitations; lanes 5 through 7, antifibrillarin immunoprecipitations; lanes 1, 2, and 8, RNA isolated from 1% of indicated total cell extracts used for immunoprecipitations.