 Transcript variant 3, RefSeq NM_022550.2, is 1735 bp and is the longest, but it also encodes for the same isoform 1 as variant 1.It contains an additional sequence in the 5’UTR of the mRNA transcript and lacks a short sequence in the 3’coding region as compared to variant 2.XRCC4 protein is a tetramer that resembles the shape of a dumbbell containing two globular ends separated by a long, thin stalk.