Final answer:
Artemis is the enzyme that cleaves interstrand hairpin structures in V(D)J recombination, with the assistance of DNA-PK, after initial cleavage by RAG-1/2.
Step-by-step explanation:
The enzyme responsible for cleaving interstrand hairpin structures during V(D)J recombination is Artemis, after the hairpins are opened by RAG-1/2. This process occurs within the coding regions of the immune system's antigen receptor genes. The answer to the question 'What cleaves interstrand hairpin in V(D)J coding regions?' is B. Artemis. The RAG-1/2 complex initiates V(D)J recombination by introducing a break in the DNA to form the hairpin structures, which are then processed by Artemis in conjunction with DNA-PK to create the necessary overhangs for successful recombination.