Exploiting the Receptor-Binding Domains of R-Spondin 1 to Target Leucine-Rich Repeat-Containin G-Coupled Protein Receptor 5-Expressing Stem Cells in Ovarian Cancer.

Leucine-rich repeat-containing G-protein-coupled receptor (LGR5) and LGR6 mark epithelial stem cells in normal tissues and tumors. They are expressed by stem cells in the ovarian surface and fallopian tube epithelia from which ovarian cancer arises. High-grade serous ovarian cancer is unique in expressing unusually high levels of LGR5 and LGR6 mRNA.

Dynamic chromatin association of IκBα is regulated by acetylation and cleavage of histone H4.

IκBs exert principal functions as cytoplasmic inhibitors of NF-kB transcription factors. Additional roles for IκB homologues have been described, including chromatin association and transcriptional regulation. Phosphorylated and SUMOylated IκBα (pS-IκBα) binds to histones H2A and H4 in the stem cell and progenitor cell compartment of skin and intestine, but the mechanisms controlling its recruitment to chromatin are largely unknown.

Therapeutic Targeting of Tumor Cells Rich in LGR Stem Cell Receptors.

LGR5 and LGR6 mark epithelial stem cells in many niches including the ovarian surface and fallopian tube epithelia from which ovarian cancer arises. Human ovarian cancers express these receptors at high levels and express one of their ligands, RSPO1, at levels uniquely higher than all other tumor types except mesothelioma. Reasoning that these receptors are also important to tumor stem cells, arming the LGR binding domain of RSPO1 with a cytotoxin may permit depletion of the tumor stem cells.

Structurally plastic NEMO and oligomerization prone IKK2 subunits define the behavior of human IKK2:NEMO complexes in solution.

The human IκB Kinase (IKK) is a multisubunit protein complex of two kinases and one scaffolding subunit that controls induction of transcription factor NF-κB activity. IKK behaves as an entity of aberrantly high apparent molecular weight in solution. Recent X-ray crystallographic and cryo-electron microscopy structures of individual catalytic subunits (IKK1/IKKα and IKK2/IKKβ) reveal that they are both stably folded dimeric proteins that engage in extensive homo-oligomerization through unique surfaces that are required for activation of their respective catalytic activities.

NF-κB, IκB, and IKK: Integral Components of Immune System Signaling.

The NF-κB (Nuclear Factor kappa B) transcription factor plays crucial roles in the regulation of numerous biological processes including development of the immune system, inflammation, and innate and adaptive immune responses. Control over the immune cell functions of NF-κB results from signaling through one of two different routes: the canonical and noncanonical NF-κB signaling pathways. Present at the end of both pathways are the proteins NF-κB, IκB, and the IκB kinase (IKK).

Genome reading by the NF-κB transcription factors.

The NF-κB family of dimeric transcription factors regulates transcription by selectively binding to DNA response elements present within promoters or enhancers of target genes. The DNA response elements, collectively known as κB sites or κB DNA, share the consensus 5'-GGGRNNNYCC-3' (where R, Y and N are purine, pyrimidine and any nucleotide base, respectively). In addition, several DNA sequences that deviate significantly from the consensus have been shown to accommodate binding by NF-κB dimers.

Protein Cofactors Are Essential for High-Affinity DNA Binding by the Nuclear Factor κB RelA Subunit.

Transcription activator proteins typically contain two functional domains: a DNA binding domain (DBD) that binds to DNA with sequence specificity and an activation domain (AD) whose established function is to recruit RNA polymerase. In this report, we show that purified recombinant nuclear factor κB (NF-κB) RelA dimers bind specific κB DNA sites with an affinity significantly lower than that of the same dimers from nuclear extracts of activated cells, suggesting that additional nuclear cofactors might facilitate DNA binding by the RelA dimers. Additionally, recombinant RelA binds DNA with relatively low affinity at a physiological salt concentration in vitro.

DNA-binding affinity and transcriptional activity of the RelA homodimer of nuclear factor κB are not correlated.

The nuclear factor κB (NF-κB) transcription factor family regulates genes involved in cell proliferation and inflammation. The promoters of these genes often contain NF-κB-binding sites (κB sites) arranged in tandem. How NF-κB activates transcription through these multiple sites is incompletely understood.

Structural Basis for the Activation of IKK1/α.

Distinct signaling pathways activate the NF-κB family of transcription factors. The canonical NF-κB-signaling pathway is mediated by IκB kinase 2/β (IKK2/β), while the non-canonical pathway depends on IKK1/α. The structural and biochemical bases for distinct signaling by these otherwise highly similar IKKs are unclear.

Chromatin-bound IκBα regulates a subset of polycomb target genes in differentiation and cancer.

IκB proteins are the primary inhibitors of NF-κB. Here, we demonstrate that sumoylated and phosphorylated IκBα accumulates in the nucleus of keratinocytes and interacts with histones H2A and H4 at the regulatory region of HOX and IRX genes. Chromatin-bound IκBα modulates Polycomb recruitment and imparts their competence to be activated by TNFα.

Alternative nuclear functions for NF-κB family members.

The NF-κB signalling pathway regulates many different biological processes from the cellular level to the whole organism. The majority of these functions are completely dependent on the activation of the cytoplasmic IKK kinase complex that leads to IκB degradation and results in the nuclear translocation of specific NF-κB dimers, which, in general, act as transcription factors. Although this is a well-established mechanism of action, several publications have now demonstrated that some members of this pathway display additional functions in the nucleus as regulators of NF-κB-dependent and independent gene expression.