title: A physical association between the human mutY homolog (hMYH) and DNA topoisomerase II-binding protein 1 (hTopBP1) regulates Chk1-induced cell cycle arrest in HEK293 cells.
abstract: BACKGROUND
  Human DNA topoisomerase II-binding protein 1 (hTopBP1) plays an important role in DNA replication and the DNA damage checkpoint pathway. The human mutY homolog (hMYH) is a base excision repair DNA glycosylase that excises adenines or 2-hydroxyadenines that are mispaired with guanine or 7,8-dihydro-8-oxoguanine (8-oxoG). hTopBP1 and hMYH were involved in ATR-mediated Chk1 activation, moreover, both of them were associated with ATR and hRad9 which known as checkpoint-involved proteins. Therefore, we investigated whether hTopBP1 interacted with hMYH, and what the function of their interaction is.
  
  
  RESULTS
  We documented the interaction between hTopBP1 and hMYH and showed that this interaction increased in a hydroxyurea-dependent manner. We also mapped the hMYH-interacting region of hTopBP1 (residues 444-991). In addition, we investigated several cell cycle-related proteins and found that co-knockdown of hTopBP1 and hMYH significantly diminished cell cycle arrest due to compromised checkpoint kinase 1 (Chk1) activation. Moreover, we observed that hMYH was essential for the accumulation of hTopBP1 on damaged DNA, where hTopBP1 interacts with hRad9, a component of the Rad9-Hus1-Rad1 complex. The accumulation of hTopBP1 on chromatin and its subsequent interaction with hRad9 lead to cell cycle arrest, a process mediated by Chk1 phosphorylation and ataxia telangiectasia and Rad3-related protein (ATR) activation.
  
  
  CONCLUSIONS
  Our results suggested that hMYH is necessary for the accumulation of hTopBP1 to DNA damage lesion to induce the association of hTopBP1 with 9-1-1 and that the interaction between hMYH and hTopBP1 is essential for Chk1 activation. Therefore, we suggest that the interaction between hMYH and hTopBP1 is crucial for activation of the ATR-mediated cell cycle checkpoint.
authors: Department of Advanced Technology Fusion, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul, 143-701 Republic of Korea.
authors: Se Hee
authors: SH
authors: Han
authors: Department of Advanced Technology Fusion, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul, 143-701 Republic of Korea.
authors: Soo-Hyun
authors: SH
authors: Hahm
authors: Department of Advanced Technology Fusion, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul, 143-701 Republic of Korea.
authors: An Hue Vy
authors: AH
authors: Tran
authors: Department of Applied Bioscience, College of Life Science, CHA University, 120 Haeryong-ro, Pocheon, Gyeonggi-do 463-836 Republic of Korea.
authors: Ji Hyung
authors: JH
authors: Chung
authors: Department of Biological Sciences, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul, 143-701 Republic of Korea.
authors: Myoung-Ki
authors: MK
authors: Hong
authors: Department of Food Science and Biotechnology of Animal Resources, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul, 143-701 Republic of Korea.
authors: Hyun-Dong
authors: HD
authors: Paik
authors: Center for Neuroscience, Korea Institute of Science and Technology, 5 Hwarang-ro 14-gil, Seongbuk-gu, Seoul, Republic of Korea.
authors: Key-Sun
authors: KS
authors: Kim
authors: Department of Advanced Technology Fusion, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul, 143-701 Republic of Korea ; College of Global Integrated Studies, Division of Interdisciplinary Studies, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul, 143-701 Republic of Korea.
authors: Ye Sun
authors: YS
authors: Han
keywords: ATR signaling; Cell cycle arrest; Human Rad9; Human mutY homolog (hMYH); Human topoisomerase II-binding protein 1 (hTopBP1); Phospho-Chk1