T4 DNA Polymerase (Cat.# M4211, M4215
) is often the enzyme of choice for removing single-stranded 3´ overhangs from double-stranded DNA fragments due the enzyme's relatively strong 3´- to 5´-exonuclease activity. In the absence of dNTPs (Cat.# U1240, U1330
), the strong exonuclease activity can degrade double-stranded DNA in addition to the single-stranded overhang. Adding 100µM dNTPs will cause the T4 DNA Polymerase to stop at the double-stranded DNA and only digest the overhang to produce a blunt end. The DNA polymerase I large Klenow fragment also has a 3´- to 5´-exonuclease activity and can be used to remove a 3´ overhang. However, the 3´- to 5´-exonuclease activity is much weaker, and thus Klenow is not commonly used for this application.