COMMON STRUCTURAL FEATURES OF THE RO RNP ASSOCIATED HY1 AND HY5 RNAS

The secondary structures of human hY1 and hY5 RNAs were determined usi ng both chemical modification techniques and enzymatic structure probi ng. The results indicate that both for hY1 and for hY5 RNA the seconda ry structure largely corresponds to the structure predicted by sequenc e alignment and computerized energy-minimization. However, some import ant deviations were observed. In the case of hY1 RNA, two regions form ing a predicted helix appeared to be single-stranded. Furthermore, the pyrimidine-rich region of hY1 RNA appeared to be very resistant to re agents under native conditions, although it was accessible to chemical reagents under semi-denaturing conditions. This may point to yet unid entified tertiary interactions for this region of hY1 RNA. In the case of hY5 RNA, two neighbouring internal loops in the predicted structur e appeared to form one large internal loop.