Abstract
HLTF (helicase-like transcription factor) is a yeast RAD5 homolog found in mammals. HLTF has E3 ubiquitin ligase and DNA helicase activities, and plays a pivotal role in the template-switching pathway of DNA damage tolerance. HLTF has an N-terminal domain that has been designated the HIRAN (HIP116 and RAD5 N-terminal) domain. The HIRAN domain has been hypothesized to play a role in DNA binding; however, the structural basis of, and functional evidence for, the HIRAN domain in DNA binding has remained unclear. Here we show for the first time the crystal structure of the HIRAN domain of human HLTF in complex with DNA. The HIRAN domain is composed of six β-strands and two α-helices, forming an OB-fold structure frequently found in ssDNA-binding proteins, including in replication factor A (RPA). Interestingly, this study reveals that the HIRAN domain interacts with not only with a single-stranded DNA but also with a duplex DNA. Furthermore, the structure unexpectedly clarifies that the HIRAN domain specifically recognizes the 3'-end of DNA. These results suggest that the HIRAN domain functions as a sensor to the 3'-end of the primer strand at the stalled replication fork and that the domain facilitates fork regression. HLTF is recruited to a damaged site through the HIRAN domain at the stalled replication fork. Furthermore, our results have implications for the mechanism of template switching.
Highlights
HLTF is responsible for template-switching of DNA damage tolerance; HLTF has a novel DNA-binding HIRAN domain, but its function is unknown
Yeast RAD5 has been shown to be an E3 ubiquitin ligase responsible for Lys-63-linked poly-ubiquitination of PCNA [4]
Mammalian cells contain two RAD5 homologs, HLTF and SHPRH (SNF2 histone-linker PHD finger RING finger helicase), both of which are involved in Lys-63linked poly-ubiquitination of PCNA at Lys-164 and in the regulation of DNA damage tolerance [5,6,7,8,9]
Summary
HLTF is responsible for template-switching of DNA damage tolerance; HLTF has a novel DNA-binding HIRAN domain, but its function is unknown. HLTF has E3 ubiquitin ligase and DNA helicase activities, and plays a pivotal role in the template-switching pathway of DNA damage tolerance. The structure unexpectedly clarifies that the HIRAN domain recognizes the 3-end of DNA These results suggest that the HIRAN domain functions as a sensor to the 3-end of the primer strand at the stalled replication fork and that the domain facilitates fork regression. Template-switching (TS) DNA synthesis, known as the damage avoidance pathway, in which one newly synthesized strand is utilized as an undamaged template for replication by replicative polymerases, is an error-free process. DNA damage tolerance is initiated by the ubiquitination of the Lys-164 of PCNA, a scaffold protein that stimulates DNA synthesis by DNA polymerases. Yeast RAD5 has been shown to be an E3 ubiquitin ligase responsible for Lys-63-linked poly-ubiquitination of PCNA [4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
