Biology subjects

Tufan, A. B.

Publications and source records attributed to Tufan, A. B..

3 recordsLinked to original sources

bioRxiv2026

Structures of MyD88 and its oncogenic mutant reveal DNA binding with implications for cytosolic DNA sensing

MyD88 is a universal adaptor that connects to Toll-like receptors and interleukin-1 receptors through its Toll/IL-1R homology (TIR) domain and activates inflammatory signaling via its death domain (DD). However, how MyD88TIR serves as the platform for these functions and if it has additional functions remain unclear. Here, we report cryogenic electron microscopy (cryo-EM) structures of MyD88TIR and its cancer-specific mutant L252P (previously L265P) mainly in ring and spiral forms, respectively. Both assemblies are formed by antiparallel double-filaments, using canonical TIR interfaces within each strand but unique surfaces between the strands, and position MyD88DD at the same sides of the assemblies for self-oligomerization and pathway activation. Surprisingly, these WT or L252P filaments are bound to dsDNA using the concave sides of the rings and the spirals. In vitro assays and cellular studies establish that MyD88 directly binds dsDNA and promotes inflammatory cytokine expression, particularly pro-IL-1{beta}, following dsDNA transfection or viral infection. Notably, these responses are unaffected by deficiency of UNC93B1, the essential chaperone required for trafficking endosomal nucleic acid-sensing TLRs. Structure-guide MyD88 mutant that disrupts dsDNA binding specifically compromises dsDNA-induced transcriptional program while maintaining TLR signaling. RNA-seq further reveals that MyD88 plays a crucial role in inducing gene expression upon dsDNA sensing and that about half of cGAS-dependent genes are also MyD88-dependent. Together, our structural, biochemical and genetic data support the findings that MyD88 directly engages with cytosolic dsDNA and cooperates with cGAS to promote the full innate immune transcriptional response.

immunology↗

bioRxiv2021

TSG101 Associates with PARP1 and is Essential for PARylation and DNA Damage-induced NF-κB Activation

In a genome-wide screening for components of the dsDNA-break-induced IKK-NF-{kappa}B pathway we identified scores of regulators, including tumor susceptibility protein TSG101. TSG101 is essential for DNA damage-induced formation of cellular poly(ADP-ribose) (PAR). TSG101 directly binds to PARP1 and is required for PARP1 activation. This function of TSG101 is independent of its role in the ESCRT-I endosomal sorting complex. In the absence of TSG101, the PAR-dependent formation of a nuclear PARP1-IKK{gamma} signalosome, which triggers IKK activation, is impaired. According to its requirement for PARP1 and NF-{kappa}B activation, TSG101 deficient cells are defective in DNA repair and apoptosis protection. Loss of TSG101 results in PARP1 trapping at damage sites and mimics the effect of pharmacological PARP-inhibition. We also show that loss of TSG101 in connection with inactivated tumor suppressors BRCA1/2 in breast cancer cells is lethal. Our results imply TSG101 as a therapeutic target to achieve synthetic lethality in cancer treatment.

molecular biology↗

bioRxiv2019

A novel IKK- and proteasome-independent mechanism of RelA activation triggers senescence associated secretome via transcriptional repression of NFKBIA

The I{kappa}B kinase (IKK) - NF-{kappa}B pathway is activated as part of the DNA damage response and controls both resistance to apoptosis and inflammation. How these different functions are achieved remained unknown. We demonstrate here that DNA double strand breaks elicit two subsequent phases of NF-{kappa}B activation in vivo and in vitro, which are mechanistically and functionally distinct. RNA-sequencing reveals that the first phase controls anti-apoptotic gene expression, while the second drives expression of senescence-associated secretory phenotype (SASP) genes. The first, rapidly activated phase is driven by the ATM-PARP1-TRAF6-IKK cascade, which triggers proteasomal destruction of I{kappa}B and is terminated through I{kappa}B (NFKBIA) re-expression. The second phase is activated days later in senescent cells but is independent of IKK and the proteasome. An altered phosphorylation status of p65, in part driven by GSK3{beta}, results in transcriptional silencing of NFKBIA and IKK-independent, constitutive activation of NF-{kappa}B in senescence. Collectively, our study reveals a novel physiological mechanism of NF-{kappa}B activation with important implications for genotoxic cancer treatment.

cell biology↗