FANCL Replaces BRCA1 as the Likely Ubiquitin Ligase Responsible for FANCD2 Monoubiquitination

Amom Ruhikanta Meetei; Zhijiang Yan; Weidong Wang

doi:10.4161/cc.3.2.656

FANCD2 and RAD51 Regulate PCNA Monoubiquitination and Translesion Synthesis

Blood ◽

10.1182/blood.v122.21.3712.3712 ◽

2013 ◽

Vol 122 (21) ◽

pp. 3712-3712

Author(s):

Gary M. Kupfer ◽

Xiaoyong Chen

Keyword(s):

Mitomycin C ◽

Ubiquitin Ligase ◽

Conflicts Of Interest ◽

E3 Ubiquitin Ligase ◽

Translesion Synthesis ◽

Deficient Mutant ◽

Independent Manner ◽

Knock Down ◽

Different Types ◽

Fancd2 Monoubiquitination

Abstract FANCD2 is a key player in Fanconi anemia (FA) pathway. It has been shown that PCNA and Rad18 can interact with FANCD2 and regulate FANCD2 monoubiquitination. Rad18 is the E3 ubiquitin ligase responsible for PCNA monoubiquitination, which is critical for PCNA function in translesion synthesis (TLS). Previous work by us and others has shown that the FA pathway interacts with PCNA and RAD18. Even though FA cells demonstrate unequivocal sensitivity to crosslinkers such as mitomycin C (MMC), we find surprisingly that they are largely resistant to hydroxyurea (HU), except for cells containing no expression of FANCD2. In order to understand the mechanism for this finding, we explored the interaction of FANCD2, Rad51, Rad18, and PCNA, which form a complex and is enhanced upon HU exposure. While FANCD2 is required, monoubiquitination of FANCD2 is not. In addition, PCNA monoubiqutination follows exactly the same pattern. The monoubiquitination of PCNA in response to HU in FANCA deficient mutant confirms that non-ubiquitinated FANCD2 can still support PCNA monoubiquitination. Rad51, but not BRCA1 is also required in regulating PCNA monoubiquitination in response to HU, suggesting that this function is independent of homologous recombination (HR). We further show that translesion polymerase Pol H chromatin localization is decreased in FANCD2 deficient cells, FANCD2 siRNA knock down cells and Rad51 siRNA knock down cells. Our data suggest that FANCD2 and Rad51 play an important role in PCNA monoubiquitination and TLS in a FANCD2 monoubiquitination and HR-independent manner in response to HU. This effect is not observed with mitomycin C (MMC) treatment, indicating that DNA repair systems differentially respond to different types of DNA damage. Disclosures: No relevant conflicts of interest to declare.

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UBE2T, the Fanconi Anemia Core Complex, and FANCD2 Are Recruited Independently to Chromatin: a Basis for the Regulation of FANCD2 Monoubiquitination

Molecular and Cellular Biology ◽

10.1128/mcb.00504-07 ◽

2007 ◽

Vol 27 (24) ◽

pp. 8421-8430 ◽

Cited By ~ 53

Author(s):

Arno Alpi ◽

Frederic Langevin ◽

Georgina Mosedale ◽

Yuichi J. Machida ◽

Anindya Dutta ◽

...

Keyword(s):

Dna Damage ◽

Ubiquitin Ligase ◽

Fanconi Anemia ◽

E3 Ubiquitin Ligase ◽

S Phase ◽

Multiprotein Complex ◽

Core Complex ◽

Nuclear Core ◽

Ubiquitin Conjugating Enzyme ◽

Fancd2 Monoubiquitination

ABSTRACT The Fanconi anemia (FA) nuclear core complex and the E2 ubiquitin-conjugating enzyme UBE2T are required for the S phase and DNA damage-restricted monoubiquitination of FANCD2. This constitutes a key step in the FA tumor suppressor pathway, and much attention has been focused on the regulation at this point. Here, we address the importance of the assembly of the FA core complex and the subcellular localization of UBE2T in the regulation of FANCD2 monoubiquitination. We establish three points. First, the stable assembly of the FA core complex can be dissociated of its ability to function as an E3 ubiquitin ligase. Second, the actual E3 ligase activity is not determined by the assembly of the FA core complex but rather by its DNA damage-induced localization to chromatin. Finally, UBE2T and FANCD2 access this subcellular fraction independently of the FA core complex. FANCD2 monoubiquitination is therefore not regulated by multiprotein complex assembly but by the formation of an active E2/E3 holoenzyme on chromatin.

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Novel players fine-tune plant trade-offs

Essays in Biochemistry ◽

10.1042/bse0580083 ◽

2015 ◽

Vol 58 ◽

pp. 83-100 ◽

Cited By ~ 25

Author(s):

Selena Gimenez-Ibanez ◽

Marta Boter ◽

Roberto Solano

Keyword(s):

Ubiquitin Ligase ◽

Feedback Loop ◽

Molecular Level ◽

26S Proteasome ◽

Signalling Molecules ◽

Transcriptional Reprogramming ◽

Trade Offs ◽

Jaz Proteins ◽

Regulatory Feedback Loop ◽

Fine Tune

Jasmonates (JAs) are essential signalling molecules that co-ordinate the plant response to biotic and abiotic challenges, as well as co-ordinating several developmental processes. Huge progress has been made over the last decade in understanding the components and mechanisms that govern JA perception and signalling. The bioactive form of the hormone, (+)-7-iso-jasmonyl-l-isoleucine (JA-Ile), is perceived by the COI1–JAZ co-receptor complex. JASMONATE ZIM DOMAIN (JAZ) proteins also act as direct repressors of transcriptional activators such as MYC2. In the emerging picture of JA-Ile perception and signalling, COI1 operates as an E3 ubiquitin ligase that upon binding of JA-Ile targets JAZ repressors for degradation by the 26S proteasome, thereby derepressing transcription factors such as MYC2, which in turn activate JA-Ile-dependent transcriptional reprogramming. It is noteworthy that MYCs and different spliced variants of the JAZ proteins are involved in a negative regulatory feedback loop, which suggests a model that rapidly turns the transcriptional JA-Ile responses on and off and thereby avoids a detrimental overactivation of the pathway. This chapter highlights the most recent advances in our understanding of JA-Ile signalling, focusing on the latest repertoire of new targets of JAZ proteins to control different sets of JA-Ile-mediated responses, novel mechanisms of negative regulation of JA-Ile signalling, and hormonal cross-talk at the molecular level that ultimately determines plant adaptability and survival.

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