During replication, if there is a lesion on DNA helix, the fork will be stalled. PCNA is monoubiquitinated and recruits the Y-family polymerases to the lesion. Herein, we investigated in the recruitment of REV1 and polymerase η to the error and interact with ubiquitinated PCNA. Other groups claimed that polymerase η contains two domains called ubiquitin zinc finger domain (UBZ) and PCNA interaction peptides box (PIP) which could bind to UbPCNA. Using NMR, we characterized the interaction of polymerase η C-terminus and ubiquitin and discovered a new ubiquitin binding box (UBB) that could bind to ubiquitin as well. Interestingly, the UBB and UBZ shared the same binding surface with ubiquitin. In addition, their function in TLS was confirmed by cell survival test. Finally, we also proposed that this binding pulls the ubiquitin closer to PCNA and make the complex more stable.