Heterogeneous polyoma giant
RNA molecules have been isolated by
oligo(dT)- cellulose chromatography during the late phase of a lytic cycle of
infection of mouse kidney cell cultures. These RNAs have sedimentation coefficients in denaturing Me2SO gradients that are greater than 26S and thus apparently correspond to
RNA molecules larger than one strand of polyoma
DNA. Approximately 15% of total nuclear polyoma late giant RNAs contained tracts of
poly(A) and were retained by
oligo(dT)-cellulose. The polyoma late giant RNAs as well as heterogeneous nuclear RNAs (HnRNAs) were found to have a slightly lower sedimentation rate in Me2SO-chloral hydrate density gradients than sedimentation values in
sucrose gradients indicated. Even when synthesis of
viral DNA and the production of
capsid protein are blocked by
5-fluorodeoxyuridine (FdU), 10% of polyoma-specific
RNA (as determined by sedimentation analyses under aqueous conditions) was shown to contain tracts of
poly(A). In contrast to our findings on polyoma late giant
RNA, nuclear polyoma
RNA synthesized in the presence of FdU sedimented in denaturing Me2SO-chloral hydrate gradients considerably slower (from 15 to 30S) in relation to
HnRNA and ribosomal
precursor RNA. The sedimentation pattern in denaturing Me2SO gradients suggest that Py
RNA synthesized late in lytic
infection in the presence of FdU may be no longer than one transcript of Py
DNA.