Cullin Explained

Symbol:Cullin
Cullin
Pfam:PF00888
Interpro:IPR001373
Prosite:PDOC00967
Scop:1ldj
Symbol:Cullin_Nedd8
Cullin protein neddylation domain
Pfam:PF10557
Interpro:IPR019559

Cullins are a family of hydrophobic scaffold proteins which provide support for ubiquitin ligases (E3). All eukaryotes appear to have cullins. They combine with RING proteins to form Cullin-RING ubiquitin ligases (CRLs) that are highly diverse and play a role in myriad cellular processes, most notably protein degradation by ubiquitination.[1] [2]

The human genome contains eight cullin genes

There is also a more distant member called ANAPC2 (or APC2), part of the Anaphase-promoting complex.

CUL1, 2, 3, 4A, 4B, 5 and 7 each form part of a multi-subunit ubiquitin complex.

Cullin-RING ubiquitin ligases

Cullin-RING ubiquitin ligases (CRLs), such as Cul1 (SCF) play an essential role in targeting proteins for ubiquitin-mediated destruction; as such, they are diverse in terms of composition and function, regulating many different processes from glucose sensing and DNA replication to limb patterning and circadian rhythms.[3] The catalytic core of CRLs consists of a RING protein and a cullin family member. For Cul1, the C-terminal cullin-homology domain binds the RING protein. The RING protein appears to function as a docking site for ubiquitin-conjugating enzymes (E2s). Other proteins contain a cullin-homology domain, such as CUL9, also known as p53 cytoplasmic anchor PARC, and the ANAPC2 subunit of the anaphase-promoting complex/cyclosome; both CUL9 and ANAPC2 have ubiquitin ligase activity. The N-terminal region of cullins is more variable, and is used to interact with specific adaptor proteins.[4] [5] [6]

Modification by NEDD8

With the exception of ANAPC2, each member of the cullin family is modified by Nedd8 and several cullins function in Ubiquitin-dependent proteolysis, a process in which the 26S proteasome recognises and subsequently degrades a target protein tagged with K48-linked poly-ubiquitin chains. Nedd8/Rub1 is a small ubiquitin-like protein, which was originally found to be conjugated to Cdc53, a cullin component of the SCF (Skp1-Cdc53/CUL1-F-box protein) E3 Ub ligase complex in Saccharomyces cerevisiae (Baker's yeast), and Nedd8 modification has now emerged as a regulatory pathway of fundamental importance for cell cycle control and for embryogenesis in metazoans. The only identified Nedd8 substrates are cullins. Neddylation results in covalent conjugation of a Nedd8 moiety onto a conserved cullin lysine residue.[7]

External links

Notes and References

  1. 10.1186/1747-1028-3-7. Cullin-RING ubiquitin ligases: Global regulation and activation cycles. 2008. Bosu. Dimple R.. Kipreos. Edward T.. Cell Division. 3. 7. 18282298. 2266742 . free .
  2. Book: Bruce, Alberts. Molecular biology of the cell. 9780815344322. Sixth . New York, NY. 887605755. 2014-11-18.
  3. Kipreos ET, Lander LE, Wing JP, He WW, Hedgecock EM . cul-1 is required for cell cycle exit in C. elegans and identifies a novel gene family . Cell . 85 . 6 . 829–39 . June 1996 . 8681378 . 10.1016/S0092-8674(00)81267-2. 15805562 . free .
  4. Petroski MD, Deshaies RJ . Function and regulation of cullin-RING ubiquitin ligases . Nat. Rev. Mol. Cell Biol. . 6 . 1 . 9–20 . January 2005 . 15688063 . 10.1038/nrm1547 . 24159190 .
  5. Zheng N, Schulman BA, Song L, Miller JJ, Jeffrey PD, Wang P, Chu C, Koepp DM, Elledge SJ, Pagano M, Conaway RC, Conaway JW, Harper JW, Pavletich NP . Structure of the Cul1-Rbx1-Skp1-F boxSkp2 SCF ubiquitin ligase complex . Nature . 416 . 6882 . 703–9 . April 2002 . 11961546 . 10.1038/416703a . 2002Natur.416..703Z . 4423882 .
  6. Goldenberg SJ, Cascio TC, Shumway SD, Garbutt KC, Liu J, Xiong Y, Zheng N . Structure of the Cand1-Cul1-Roc1 complex reveals regulatory mechanisms for the assembly of the multisubunit cullin-dependent ubiquitin ligases . Cell . 119 . 4 . 517–28 . November 2004 . 15537541 . 10.1016/j.cell.2004.10.019 . 1606360 . free .
  7. Pan ZQ, Kentsis A, Dias DC, Yamoah K, Wu K . Nedd8 on cullin: building an expressway to protein destruction . Oncogene . 23 . 11 . 1985–97 . March 2004 . 15021886 . 10.1038/sj.onc.1207414 . free .