Mutations in the human RecQ helicase, BLM, causes Bloom Syndrome, which is a rare autosomal recessive disorder and characterized by genomic instability and an increased risk of cancer. Fanconi Anemia (FA), resulting from mutations in any of the 19 known FA genes and those yet to be known, is also characterized by chromosomal instability and a high incidence of cancer. BLM helicase and FA proteins, therefore, may work in a common tumor-suppressor signaling pathway. To date, it remains largely unclear as to how BLM and FA proteins work concurrently in the maintenance of genome stability. Here we report that BLM is involved in the early activation of FA group D2 protein (FANCD2). We found that FANCD2 activation is substantially delayed and attenuated in crosslinking agent-treated cells harboring deficient Blm compared to similarly treated control cells with sufficient BLM. We also identified that the domain VI of BLM plays an essential role in promoting FANCD2 activation in cells treated with DNA crosslinking agents, especially ultraviolet B. The similar biological effects performed by ΔVI-BLM and inactivated FANCD2 further confirm the relationship between BLM and FANCD2. Mutations within the domain VI of BLM detected in human cancer samples demonstrate the functional importance of this domain, suggesting human tumorigenicity resulting from mtBLM may be at least partly attributed to mitigated FANCD2 activation. Collectively, our data show a previously unknown regulatory liaison in advancing our understanding of how the cancer susceptibility gene products act in concert to maintain genome stability.

Extremely high cancer incidence associated with patients with Fanconi anemia (FA) suggests the importance of the FA signaling pathway in the suppression of non-FA human tumor development. Indeed, we found that an impaired FA signaling pathway substantially contributes to the development of non-FA human tumors. However, the mechanisms underlying the function of the FA pathway remain less understood. Using RNA interfering approach in combining with cell proliferation and reporter assays, we showed that the function of FA signaling pathway is at least partly mediated through coupling with hRad6/hRad18 signaling (HHR6 pathway). We previously reported that FANCD2 monoubiquitination, a hallmark of the FA pathway activation, can be regulated by HHR6. Here we found that hRad18 can also regulate activation of the FA pathway. More importantly, we found that FANCD2 is capable of modulating activity of DNA translesion synthesis polymerase eta, an effector of HHR6 pathway. These results provide novel insights into how the FA pathway is intertwined with HHR6 pathway to maintain chromosomal stability and suppress the development of human cancer, representing an important conceptual advance in the field of FA cancer research.

Effectiveness of DNA cross-linking drugs in the treatment of bladder cancer suggests that bladder cancer cells may have harbored an insufficient cellular response to DNA cross-link damage, which will sensitize cells to DNA cross-linking agents. Cell sensitivity benefits from deficient DNA damage responses, which, on the other hand, can cause cancer. Many changed cellular signaling pathways are known to be involved in bladder tumorigenesis; however, DNA cross-link damage response pathway [Fanconi anemia (FA) pathway], whose alterations appear to be a plausible cause of the development of bladder cancer, remains an under-investigated area in bladder cancer research. In this study, we found FAVL (variant of FA protein L--FANCL) was elevated substantially in bladder cancer tissues examined. Ectopic expression of FAVL in bladder cancer cells as well as normal human cells confer an impaired FA pathway and hypersensitivity to Mitomycin C, similar to those found in FA cells, indicating that FAVL elevation may possess the same tumor promotion potential as an impaired FA pathway harbored in FA cells. Indeed, a higher level of FAVL expression can promote the growth of bladder cancer cells in vitro and in vivo, which, at least partly, results from FAVL perturbation of FANCL expression, an essential factor for the activation of the FA pathway. Moreover, a higher level of FAVL expression was found to be associated with chromosomal instability and the invasiveness of bladder cancer cells. Collectively, FAVL elevation can increase the tumorigenic potential of bladder cancer cells, including the invasive potential that confers the development of advanced bladder cancer. These results enhance our understanding the pathogenesis of human bladder cancer, holding a promise to develop additional effective tools to fight human bladder cancer.

As important immunosuppressive viruses, chicken infectious anemia virus (CIAV) and subgroup J avian leukosis virus (ALV-J) have caused huge economic losses to the poultry industry globally. Recently, the co-infection of CIAV and ALV-J frequently occurred in the domestic chicken flocks in China. However, the synergistic pathogenesis of CIAV and ALV-J has not been fully investigated. Here, a co-infection study was performed to further understand the potential synergistic pathogenesis of CIAV and ALV-J. In vitro study showed that CIAV could promote the replication of ALV-J in HD11 cells, but ALV-J could not increase the replication of CIAV. Chicken infection study showed both CIAV and ALV-J with synergistic effects caused significant body weight loss to the infected chickens. Although ALV-J had no effect on CIAV viral shedding and tissue load, CIAV did significantly increase ALV-J viremia, viral shedding and tissue load in the co-infection group. Moreover, both CIAV and ALV-J could significantly inhibit the humoral immunity to H9N2 influenza virus and serotype 4 fowl adenovirus (FAdV-4). All these data demonstrate the synergistic pathogenesis for the co-infection of CIAV and ALV-J, and highlight the positive effect of CIAV on the pathogenesis of ALV-J.

Platinum compounds have been widely used as a primary treatment for many types of cancer. However, resistance is the major cause of therapeutic failure for patients with metastatic or recurrent disease, thus highlighting the need to identify novel factors driving resistance to Platinum compounds. Metadherin (MTDH, also known as AEG-1 and LYRIC), located in a frequently amplified region of chromosome 8, has been consistently associated with resistance to chemotherapeutic agents, though the precise mechanisms remain incompletely defined.

Emerging Fanconi Anemia (FA) signaling in the field of cancer research annotates the extreme importance of its center player, Fanconi Anemia complementation group D2 (FANCD2) in protecting human cells from going awry. However, a previously-unrecognized form of FANCD2, namely FANCD2-V2, is understudied. We report TRK-Fused Gene (TFG) is critical for roles played by FANCD2-V2 in early responses to DNA damage, but not for FANCD2-V1, the long-known form of FANCD2. FANCD2-V2 forms nuclear foci upon DNA damage, and both its focus appearance and disappearance are earlier than FANCD2-V1. The amino acid/aa 5-100 of TFG and the aa1437-1442 of FANCD2-V2 were identified to contribute to their interaction, which maintains the steady-state level of FANCD2-V2 protein. TFGΔaa5-100 or FANCD2-V2Δaa1437-1442-carrying cells could not show timely focus formation of FANCD2-V2 upon DNA damage and gained carcinogenicity over time. This study provides a previously-unknown key to unlock in-depth insights into maintaining genome stability, fostering translational studies on preventing, diagnosing and/or treating related diseases.

Poly(ADP-ribose) polymerase inhibitors (PARPis) are U.S. Food and Drug Administration (FDA) approved for treatment of BRCA-mutated metastatic breast cancer. Furthermore, the BROCADE studies demonstrated benefit of adding an oral PARPi, veliparib, to carboplatin and paclitaxel in patients with metastatic breast cancer harboring BRCA mutation. Given multiple possible dosing schedules and the potential benefit of this regimen for patients with defective DNA repair beyond BRCA, we sought to find the recommended phase II dose (RP2D) and schedule of veliparib in combination with carboplatin in patients with advanced breast cancer, either triple-negative (TNBC) or hormone receptor (HR)-positive, human epidermal growth receptor 2 (HER2) negative with defective Fanconi anemia (FA) DNA-repair pathway based on FA triple staining immunofluorescence assay.

Chicken infectious anemia virus (CIAV) mainly infects chickens and causes immunosuppression. In this study, a CIAV isolate, designated as Pigeon-CIAV-1906, was efficiently isolated from two sick pigeons by inoculating the samples into MSB1 cells. The genome of Pigeon-CIAV-1906 was amplified by PCR and analyzed. The genome size of Pigeon-CIAV-1906 was 2,298 bp with the highest homology (99.5%) to Jilin strain (JL14023) and the lowest homology (91.5%) to Brazil strain (KY024579), which phylogenetically clustered into Group A. Notably, several amino acids such as 139K and 394Q related with high virulence were found in the VP1 of Pigeon-CIAV-1906. The isolation of Pigeon-CIAV-1906 and its molecular characteristics provide evidence for the cross-transmission of CIAV from chicken to pigeon and give novel insights into the molecular epidemiology of CIAV.

How Fanconi anemia (FA) protein D2 (FANCD2) performs DNA damage repair remains largely elusive. We report here that translesion synthesis DNA polymerase (pol) eta is a novel mediator of FANCD2 function. We found that wild type (wt) FANCD2, not K561R (mt) FANCD2, can interact with pol eta. Upon DNA damage, the interaction of pol eta with FANCD2 occurs earlier than that with PCNA, which is in concert with our finding that FANCD2 monoubiquitination peaks at an earlier time point than that of PCNA monoubiquitination. FANCD2-null FA patient cells (PD20) carrying histone H2B-fused pol eta and wtFANCD2, respectively, show a similar tendency of low Mitomycin C (MMC) sensitivity, while cells transfected with empty vector control or pol eta alone demonstrate a similar high level of MMC sensitivity. It therefore appears that FANCD2 monoubiquitination plays a similar anchor role as histone to bind DNA in regulating pol eta. Collectively, our study indicates that, in the early phase of DNA damage response, FANCD2 plays crucial roles in recruiting pol eta to the sites of DNA damage for repair.

A compromised Fanconi Anemia (FA) signaling pathway, often resulting from an inactivated FANCD2, was recently recognized to contribute to the development of non-FA human tumors. However, it is largely unknown as to how an impaired FA pathway or an inactivated FANCD2 promotes tumorigenesis. Here we unexpectedly found that ΔNp63 mRNA was expressed at high levels in human cancer cells carrying an impaired FA pathway compared to the corresponding control cells carrying an intact FA pathway. This observation was recapitulated upon conditionally managing the status of FANCD2 monoubiquitination /activation in 293T cells. Importantly, ΔNp63 elevation upon FANCD2 inactivation was confirmed in human fibroblasts derived from FA patients. Moreover, we have identified a 189 bp DNA fragment downstream of the ΔNp63 promoter (P2) that can mediate the upregulation of ΔNp63 by an inactivated FANCD2, and determined that elevated ΔNp63 is high enough to promote cancer cell proliferation and metastasis. In vivo, the elevation of FAVL, a tumor promotion factor that inhibits FANCD2 activation, was found to be positively associated with ΔNp63 expression in human cancer tissues. Collectively, these results document a novel role of an inactivated FANCD2 in upregulating ΔNp63, advancing our understanding of how an impaired FA pathway contributes to the pathogenesis of human cancer.

Normal DNA replication starts following the stepwise recruitment of replication initiators to assemble Mini-chromosome Maintenance (MCM) 2-7 protein complexes at an adequate amount of DNA replication origins. Under normal conditions, the monoubiquitination of Fanconi Anemia (FA) group D2 protein (FANCD2) occurs in each S-phase of cell cycle, which is the basal level of FANCD2 monoubiquitination. However, little is known regarding the roles of this basal level of monoubiquitinated FANCD2. Here we show that monoubiquitinated FANCD2 in each S-phase of normal cell cycle is essential for replication origins to fire at a normal rate. We found that the basal level of the monoubiquitinated FANCD2 can interact with replication origins as well as mini-chromosome maintenance protein 3 (MCM3) in an S-phase specific manner to secure an enough number of the licensed-origins to fire. Non-monoubiquitinated FANCD2 or mutant MCM3 lacking AA 477-480 responsible for interacting with FANCD2 can lead to an insufficient amount of licensed origins to fire and, thereby, enlarged intervals between the fired origins. Our results demonstrate that the monoubiquitinated FANCD2 in each S-phase of normal cell cycle is required to maintain an enough number of licensed origins to initiate the normal DNA replication. This finding is the first to provide insights into how FANCD2 functions under normal condition of cell cycle to maintain genome stability, as well as resulting implications in the strategic improvement for the fight against human cancer.

Fanconi Anemia (FA) complementation group D2 protein (FANCD2) is the center of the FA tumor suppressor pathway, which has become an important field of investigation in human aging and cancer. Here we report an overlooked central player in the FA pathway, FANCD2 variant 2 (FANCD2-V2), which appears to perform more potent tumor suppressor-function compared to the known variant of FANCD2, namely, FANCD2-V1. Detailed analysis of the FANCD2 gene structure indicated a proximal and distal polyadenylation site (PAS), associated with V2 and V1 transcripts accordingly. RNA polymerase II Chromatin immunoprecipitation (ChIP) targeting the two PAS-regions determined lesser binding of RNA pol II to DNA fragments in the distal PAS region in non-malignant cells compared to malignant cells. Conversely, the opposite occurred in the proximal PAS region. Moreover, RNA immunoprecipitation (RIP) identified that U2 snRNP, a major component of RNA splicing complex that interacts with the 3'end of an intron, showed greater binding to the last intron of the FANCD2-V1 transcript in malignant cells compared to the non-malignant cells. Importantly, our data showed that in human tissue samples, the ratio of V2 /V1 expression in lung, bladder, or ovarian cancer correlates inversely with the tumor stages/grades. Therefore, these findings provide a previously unrecognized central player FANCD2-V2 and thus novel insights into human tumorigenesis, and indicate that V2/V1 can act as an effective biomarker in assisting the recognition of tumor malignance.