Chloroplast ribonucleoproteins are associated with both mRNAs and intron-containing precursor tRNAs.

Tobacco chloroplasts possess five conserved ribonucleoproteins (cpRNPs). To elucidate the function of cpRNPs we analyzed their localization and target nucleic acid molecules in chloroplasts. Immunoprecipitation of the stromal extract and Northern analysis revealed that cpRNPs are associated in vivo with not only various species of chloroplast mRNAs but also intron-containing precursor (pre-) tRNAs. This observation strongly suggests that cpRNPs are involved in RNA processing, including mRNA stability and pre-tRNA splicing.