[Affinity modification of 80S ribosomes from human placenta with mRNA analogs--derivatives of oligouridylates with alkylating groups at the 3'-end].

2',3'-O-[4-(N-2-chloroethyl-N-methylamino)]benzylidene derivatives of oligoribonucleotides (Up)5U[32P]pC and (Up)11U[32P]pC were used for affinity labeling of 80S ribosomes from human placenta in the presence of cognate Phe-tRNA(Phe). The derivatives retained the ability of tRNA(Phe)-dependent binding with 80S ribosomes and within the corresponding complexes were cross-linked to 40S subunits (preferentially to 18S rRNA). Sites of the mRNA analogs attachment were identified by blot-hybridization of the modified rRNA with restriction fragments of corresponding rDNA. They are located within positions 1610-1747 and 1748-1865 for both analogs. These fragments are situated at the 3'-end region of 18S rRNA in a highly conserved part of eukaryotic small subunit rRNA secondary structure.