KINETIC ANALYSES OF DNA-LINKED RIBONUCLEASES-H WITH DIFFERENT SIZES OF DNA

A series of DNA-linked ribonucleases H with DNA adducts varying in siz e and sequence, ranging from heptamer to nonamer, were constructed and examined for their ability to cleave the 12-base RNA (5'-CGGAGAUGACGG -3') site-specifically. The DNA-linked RNase H with the 9-base DNA (5' -GTCATCTCC-3') cleaved the 12-base RNA specifically at A6-U7. Kinetic studies revealed that the DNA-linked RNase H with the 8-base DNA (5'-T CATCTCC-3') cleaved it sightly more effectively than that with the 9-b ase DNA. Factors that may affect the specificity and catalytic efficie ncy of a DNA-linked RNase H are described.