No, short ends 4 bp or less are not good substrates. Use DNA Polymerase I, Large (Klenow) Fragment (NEB# M0210) to fill in 5' overhangs (also called 3' recessed ends) and chew back 3' overhangs or use Mung Bean Nuclease (NEB# M0250) to chew back 3' or 5' overhangs. Note: 3' overhangs cannot be filled in.