Abstract
A homogeneous RNA complex with a sedimentation coefficient of 70 S and an apparent molecular weight of approximately 6.1 × 10(6) was released from purified (32)P-labeled, mouse-brain-derived OC-43 virus after treatment with 1% sodium dodecyl sulfate (SDS) for 15 min at 23°. The complex was highly susceptible to heat, releasing 4 S RNA fragments at 37° and breaking down to fragments of 4–70 S at 60°; it was also degraded by centrifugation through dimethyl sulfoxide gradients. Unlike tobacco mosaic virus or Rous sarcoma virus RNA, OC-43 RNA prepared by extraction with phenol-SDS or phenol-chloroform degraded into a range of fragments with coefficients of 15–55 S; 4 S RNA was also present as a minor component. This suggests that (a) extensive nicking of a large RNA molecule has occurred during viral growth, due to ribonucleases which are inactivated during phenol extractions; (b) heterogeneity for OC-43 RNA is not due to internal ribonuclease activity and fragments are held together by noncovalent linkages much weaker than those present in the 70 S retroviral RNA complex, or by small proteins; or, most probably, (c) a combination of extensive nicking and weak noncovalent linkages results in the heterogeneous denaturation products.