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작성일 : 12-05-04 10:04
5/10(목) 화학과 세미나 안내
 글쓴이 : 응용화학과
조회 : 479  
* 일시 : 20125월 10일 목요일 오후 430
* 장소 : 공학관 107
* 연사 : 이상호 교수 [성균관대학교 생명과학과]
* 주제 : Recognition of linkage-specific polyubiquitin chains by two A20-type zinc finger-containing proteins
* 초록 :
Recognition of linkage-specific polyubiquitin chains by two A20-type zinc finger-containing proteins

Sangho Lee
Department of Biological Sciences, Sungkyunkwan University

Polyubiquitination with different linkages plays crucial roles in regulating many proteolytic and non-proteolytic functions in cell. A20-type zinc finger domains (A20_ZFs) in animals reportedly recognize ubiquitin, either mono- or poly-ubiquitin. While monoubiquitin recognition by animal A20_ZFs has been extensively characterized biochemically, studies on polyubiquitin recognition lag behind. An A20_ZF from A20, a protein involved in NF-κB signaling, was shown to selectively bind K63-linked polyubiquitin. However, it remains elusive if A20_ZFs in homologous proteins exhibit similar linkage-specificity in polyubiquitin binding. Also, it is unclear whether A20_ZFs in plants perform similar roles. To address these questions, we employed A20_ZFs from bovine Rabex-5 and Arabidopsis stress associated protein 5 (AtSAP5) to explore linkage-specific polyubiquitin recognition by the two A20_ZF-containing proteins. Rabex-5 regulates endosomal trafficking via its tandem ubiquitin binding domains (A20_ZF and MIU). AtSAP5 is involved with abiotic stress response in plants and contains A20_ZF and AN1-type zinc finger domain. GST pulldown assay reveals that the N-terminal fragment of Rabex-5 harboring A20_ZF and MIU, termed Rabex-5(9-73), shows similar preference for linear, K63-linked, and K48-linked polyubiquitin binding while AtSAP5 less preference for K48-linked one. Mutagenesis analysis indicates that the A20_ZF domain of AtSAP5 is sufficient for linkage-specific polyubiquitin recognition. In contrast, A20_ZF of Rabex-5(9-73) appears dispensable for linkage-specific polyubiquitin binding. The dialipathic patch in AtSAP5, distinct from the conserved diaromatic patch in Rabex-5, seems to be responsible for K48-linked polyubiquitin binding. Taken together, our results suggest that A20_ZFs in Rabex-5 and AtSAP5 show linkage-specific preferences distinct from that of A20. We also establish that A20_ZF in plants participates in polyubiquitin recognition just like its counterparts in animals.
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