High-mobility group boxes mediate cell proliferation and radiosensitivity via retinoblastoma-interaction-dependent and -independent mechanisms.
Our previous studies have shown that high-mobility group box 1 (HMGB1) could physically associate with the retinoblastoma (RB) protein via an LXCXE (leucine-X-cysteine-X-glutamic; X=any amino acid) motif. An identical LXCXE motif is present in the HMGB1-3 protein sequences, whereas a near-consensus LXCXD (leucine-X-cysteine-X-asparagine; X=any amino acid) motif is found in the HMGB4 protein. In this study, we have demonstrated that like HMGB1, HMGB2-3 also associated with the RB in vitro and in vivo, as evidenced by glutathione-s-transferase capture and immunoprecipitation-Western blot assays. A point mutation of the LXCXE or LXCXD motif led to disruption of RB:HMGB1-4 interactions. Enforced expression of HMGB1-3 or HMGB4 by adenoviral-vector-mediated gene transfer resulted in significant inhibition of breast cancer cell proliferation through an LXCXE- or LXCXD-dependent mechanism and an increased radiosensitivity through an LXCXE- or LXCXD-independent mechanism. These results suggest an important role of the LXCXE/D motif in RB:HMGB1-4 association and modulation of cancer cell growth, but not radiosensitivity.
Department of Radiotherapy, The First Affiliated Hospital of Soochow University, Suzhou, China.
Li-Li
LL
Wang
Qing-Hui
QH
Meng
Yang
Y
Jiao
Jia-Ying
JY
Xu
Chun-Min
CM
Ge
Ju-Ying
JY
Zhou
Eliot M
EM
Rosen
Hai-Chao
HC
Wang
Sai-Jun
SJ
Fan
D000595:Amino Acid Sequence; D001665:Binding Sites; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy; D048708:Cell Growth Processes / Q000502:physiology; D045744:Cell Line, Tumor; D005260:Female; D006609:High Mobility Group Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D011836:Radiation Tolerance; D012175:Retinoblastoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D006609:High Mobility Group Proteins; D016160:Retinoblastoma Protein