Inhibitory action of different RNA fractions on the translation of globin mRNA in vitro.

Preparations of 28S rRNA and 12S RNA, obtained from sheep lymphocytes, were shown to inhibit the translation of globin mRNA. An inhibition by a given amount of 12S or 28S RNA was only obvious at saturating or near saturating levels of globin mRNA, suggesting that the inhibitory RNAs interacted with some factor essential for protein synthesis other than mRNA. The inhibitory RNAs had no effect on the translation of the synthetic template polyuridylic acid. It is suggested therefore that the target for inhibitory RNAs might be a natural mRNA specific initiation factor.