Transcription factor RFX7 governs a tumor suppressor network in response to p53 and stress.

Despite its prominence, the mechanisms through which the tumor suppressor p53 regulates most genes remain unclear. Recently, the regulatory factor X 7 (RFX7) emerged as a suppressor of lymphoid neoplasms, but its regulation and target genes mediating tumor suppression remain unknown. Here, we identify a novel p53-RFX7 signaling axis. Integrative analysis of the RFX7 DNA binding landscape and the RFX7-regulated transcriptome in three distinct cell systems reveals that RFX7 directly controls multiple established tumor suppressors, including PDCD4, PIK3IP1, MXD4, and PNRC1, across cell types and is the missing link for their activation in response to p53 and stress. RFX7 target gene expression correlates with cell differentiation and better prognosis in numerous cancer types. Interestingly, we find that RFX7 sensitizes cells to Doxorubicin by promoting apoptosis. Together, our work establishes RFX7's role as a ubiquitous regulator of cell growth and fate determination and a key node in the p53 transcriptional program.

Interplay of RFX transcription factors 1, 2 and 3 in motile ciliogenesis.

Cilia assembly is under strict transcriptional control during animal development. In vertebrates, a hierarchy of transcription factors (TFs) are involved in controlling the specification, differentiation and function of multiciliated epithelia. RFX TFs play key functions in the control of ciliogenesis in animals. Whereas only one RFX factor regulates ciliogenesis in C. elegans, several distinct RFX factors have been implicated in this process in vertebrates. However, a clear understanding of the specific and redundant functions of different RFX factors in ciliated cells remains lacking. Using RNA-seq and ChIP-seq approaches we identified genes regulated directly and indirectly by RFX1, RFX2 and RFX3 in mouse ependymal cells. We show that these three TFs have both redundant and specific functions in ependymal cells. Whereas RFX1, RFX2 and RFX3 occupy many shared genomic loci, only RFX2 and RFX3 play a prominent and redundant function in the control of motile ciliogenesis in mice. Our results provide a valuable list of candidate ciliary genes. They also reveal stunning differences between compensatory processes operating in vivo and ex vivo.

Zebrafish Rfx4 controls dorsal and ventral midline formation in the neural tube.

BACKGROUND: Rfx winged-helix transcription factors, best known as key regulators of core ciliogenesis, also play ciliogenesis-independent roles during neural development. Mammalian Rfx4 controls neural tube morphogenesis via both mechanisms. RESULTS: We set out to identify conserved aspects of rfx4 gene function during vertebrate development and to establish a new genetic model in which to analyze these mechanisms further. To this end, we have generated frame-shift alleles in the zebrafish rfx4 locus using CRISPR/Cas9 mutagenesis. Using RNAseq-based transcriptome analysis, in situ hybridization and immunostaining we identified a requirement for zebrafish rfx4 in the forming midlines of the caudal neural tube. These functions are mediated, least in part, through transcriptional regulation of several zic genes in the dorsal hindbrain and of foxa2 in the ventral hindbrain and spinal cord (floor plate). CONCLUSIONS: The midline patterning functions of rfx4 are conserved, because rfx4 regulates transcription of foxa2 and zic2 in zebrafish and in mouse. In contrast, zebrafish rfx4 function is dispensable for forebrain morphogenesis, while mouse rfx4 is required for normal formation of forebrain ventricles in a ciliogenesis-dependent manner. Collectively, this report identifies conserved aspects of rfx4 function and establishes a robust new genetic model for in-depth dissection of these mechanisms. Developmental Dynamics 247:650-659, 2018. © 2017 Wiley Periodicals, Inc.

Transcription Factor RFX2 Is a Key Regulator of Mouse Spermiogenesis.

The regulatory factor X (RFX) family of transcription factors is crucial for ciliogenesis throughout evolution. In mice, Rfx1-4 are highly expressed in the testis where flagellated sperm are produced, but the functions of these factors in spermatogenesis remain unknown. Here, we report the production and characterization of the Rfx2 knockout mice. The male knockout mice were sterile due to the arrest of spermatogenesis at an early round spermatid step. The Rfx2-null round spermatids detached from the seminiferous tubules, forming large multinucleated giant cells that underwent apoptosis. In the mutants, formation of the flagellum was inhibited at its earliest stage. RNA-seq analysis identified a large number of cilia-related genes and testis-specific genes that were regulated by RFX2. Many of these genes were direct targets of RFX2, as revealed by chromatin immunoprecipitation-PCR assays. These findings indicate that RFX2 is a key regulator of the post-meiotic development of mouse spermatogenic cells.