[Re-expression of various i-antigens in Dileptus anser after temporary transformation of serotype]

RNP particles containing 20S prosomes (alpha RNP) isolated from human epidermoid carcinoma cell line A-431 are shown to posses strong and regulated endonuclease activity specific for high-molecular-weight RNA, particularly, specific mRNAs. Furthermore, alpha-RNP destabilize the 3'-untranslated regions of c-myc mRNA, creating a specific cleavage pattern. Cleavage point within Alu sequence in high-molecular-weight RNA has been localized by primer-extension method. This RNase activity is induced under the action of EGF. alpha-RNP involvement in the coordinated control of processing and stability of specific messenger RNA molecules is suggested. The endoribonuclease activity of alpha-RNP can represent a link between EGF signalling pathway and RNA processing and degradation.