Overexpressed FOXM1 collaborates with MMB to increase WEE1 inhibitor sensitivity in NSCLC.

Background: Non-small cell lung cancer (NSCLC) is a common lung tumor with high mortality. The complex formed by MYB-MuvB complex (MMB) and forkhead box M1 (FOXM1) (MMB-FOXM1) plays a vital role in cell cycle progression to affect the progression of diseases. The role of the FOXM1-MMB complex in Wee1-like protein kinase (WEE1) inhibitor sensitivity in NSCLC keeps unclear. Methods: The reverse transcription quantitative polymerase chain reaction (RT-qPCR) was performed to measure the mRNA levels of FOXM1, LIN54, Replication Protein A (RPA), gammaH2AX (γH2AX) and Cyclin B (CCNB). The western blot was performed to examine the corresponding protein expressions. The Cell Counting Kit-8 (CCK-8) assay was performed to test cell survival. Result: It was demonstrated that after AZD-1775 treatment, the decrease in cell survival mediated by FOXM1 overexpression (P<0.001) could be reversed by LIN54 knockdown (P<0.01) and that cell survival in the control group did not differ obviously from that in the pcDNA3.1-FOXM1+siLIN54 group, indicating that the FOXM1-MMB complex was necessary for WEE1 inhibitor sensitivity. Moreover, the mRNA and protein expression levels of RPA and γH2AX were increased after AZD-1775 treatment and FOXM1 overexpression (P<0.01), suggesting that FOXM1 upregulation enhanced DNA replication stress and DNA damage. Finally, we found that the increases in the mRNA and protein expression levels of CCNB mediated by FOXM1 (P<0.01) could be rescued by silencing LIN54 (P<0.001) and that CCNB expression in the control group did not differ obviously from that in the pcDNA3.1-FOXM1+siLIN54 group. These findings revealed that the FOXM1-MMB complex activated G2/M checkpoints. In our work, it was discovered that FOXM1 overexpression increased DNA replication stress, which increased DNA replication and pressure on the WEE1 checkpoint. On the other hand, FOXM1 can enhance CCNB expression, increase the threshold content of the CCNB/CDK1 complex, facilitate mitosis, and promote WEE1 dephosphorylation. Under these two conditions, sensitivity to the WEE1 inhibitor AZD-1775 is increased, which leads to the accumulation of DNA damage and drives the activation of apoptosis. Conclusions: Overexpressed FOXM1 collaborates with MMB to increase WEE1 inhibitor sensitivity in NSCLC. This discovery might highlight the regulatory function of FOXM1/MMB in the treatment of NSCLC patients.

Coordinating gene expression during the cell cycle.

Cell cycle-dependent gene transcription is tightly controlled by the retinoblastoma (RB):E2F and DREAM complexes, which repress all cell cycle genes during quiescence. Cyclin-dependent kinase (CDK) phosphorylation of RB and DREAM allows for the expression of two gene sets. The first set of genes, with peak expression in G1/S, is activated by E2F transcription factors (TFs) and is required for DNA synthesis. The second set, with maximum expression during G2/M, is required for mitosis and is coordinated by the MuvB complex, together with B-MYB and Forkhead box M1 (FOXM1). In this review, we summarize the key findings that established the distinct control mechanisms regulating G1/S and G2/M gene expression in mammals and discuss recent advances in the understanding of the temporal control of these genes.

Silencing the alternative.

The transcription factor ztf-11 promotes neuronal differentiation by repressing other cell fates in the nematode worm C. elegans.

A Myt1 family transcription factor defines neuronal fate by repressing non-neuronal genes.

Cellular differentiation requires both activation of target cell transcriptional programs and repression of non-target cell programs. The Myt1 family of zinc finger transcription factors contributes to fibroblast to neuron reprogramming in vitro. Here, we show that ztf-11 (Zinc-finger Transcription Factor-11), the sole Caenorhabditis elegans Myt1 homolog, is required for neurogenesis in multiple neuronal lineages from previously differentiated epithelial cells, including a neuron generated by a developmental epithelial-to-neuronal transdifferentiation event. ztf-11 is exclusively expressed in all neuronal precursors with remarkable specificity at single-cell resolution. Loss of ztf-11 leads to upregulation of non-neuronal genes and reduced neurogenesis. Ectopic expression of ztf-11 in epidermal lineages is sufficient to produce additional neurons. ZTF-11 functions together with the MuvB corepressor complex to suppress the activation of non-neuronal genes in neurons. These results dovetail with the ability of Myt1l (Myt1-like) to drive neuronal transdifferentiation in vitro in vertebrate systems. Together, we identified an evolutionarily conserved mechanism to specify neuronal cell fate by repressing non-neuronal genes.

The transcription factor p53: not a repressor, solely an activator.

The predominant function of the tumor suppressor p53 is transcriptional regulation. It is generally accepted that p53-dependent transcriptional activation occurs by binding to a specific recognition site in promoters of target genes. Additionally, several models for p53-dependent transcriptional repression have been postulated. Here, we evaluate these models based on a computational meta-analysis of genome-wide data. Surprisingly, several major models of p53-dependent gene regulation are implausible. Meta-analysis of large-scale data is unable to confirm reports on directly repressed p53 target genes and falsifies models of direct repression. This notion is supported by experimental re-analysis of representative genes reported as directly repressed by p53. Therefore, p53 is not a direct repressor of transcription, but solely activates its target genes. Moreover, models based on interference of p53 with activating transcription factors as well as models based on the function of ncRNAs are also not supported by the meta-analysis. As an alternative to models of direct repression, the meta-analysis leads to the conclusion that p53 represses transcription indirectly by activation of the p53-p21-DREAM/RB pathway.