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Many components of the circadian molecular clock are conserved from flies to mammals; however, the role of mammalian Timeless remains ambiguous. Here, we report a mutation in the human TIMELESS (hTIM) gene that causes familial advanced sleep phase (FASP). Tim CRISPR mutant mice exhibit FASP with altered photic entrainment but normal circadian period. We demonstrate that the mutation prevents TIM accumulation in the nucleus and has altered affinity for CRY2, leading to destabilization of PER/CRY complex and a shortened period in nonmature mouse embryonic fibroblasts (MEFs). We conclude that TIM, when excluded from the nucleus, can destabilize the negative regulators of the circadian clock, alter light entrainment, and cause FASP.

Background The rhythmic mating behavior of insects has been extensively documented, yet the regulation of this behavior through sex pheromone sensing olfactory genes affected by the clock genes in the rhythm pathway remains unclear. Results In this study, we investigated the impact of circadian rhythm on female recognition of male rectal Bacillus -produced sex pheromone in B. dorsolis . Behavioral and electrophysiological assays revealed a peak in both mating behavior and response to sex pheromones in the evening in females. Comparative transcriptome analysis of female heads demonstrated rhythmic expression of the Timeless gene-Tim and odorant binding protein gene-Pbp5, with the highest expression levels occurring in the evening. Protein structural modeling, tissue expression patterns, RNAi treatment, and physiological/behavioral studies supported Pbp5 as a sex pheromone binding protein whose expression is affected by Tim. Furthermore, manipulation of the female circadian rhythm resulted in increased morning mating activity, accompanied by consistent peak expression of Tim and Pbp5 during this time period. These findings provide evidence that insect mating behavior can be modulated by clock genes through their effects on sex pheromone sensing processes. Conclusions Our results also contribute to a better understanding of the molecular mechanisms underlying rhythmic insect mating behavior.

Cryptochromes (CRYs) entrain the circadian clocks of plants and animals to light. Irradiation of the Drosophila cryptochrome (dCRY) causes reduction of an oxidized flavin cofactor by a chain of conserved tryptophan (Trp) residues. However, it is unclear how redox chemistry within the Trp chain couples to dCRY-mediated signaling. Here, we show that substitutions of four key Trp residues to redox-active tyrosine and redox-inactive phenylalanine tune the light sensitivity of dCRY photoreduction, conformational activation, cellular stability, and targeted degradation of the clock protein timeless (TIM). An essential surface Trp gates electron flow into the flavin cofactor, but can be relocated for enhanced photoactivation. Differential effects of Trp-mediated flavin photoreduction on cellular turnover of TIM and dCRY indicate that these activities are separated in time and space. Overall, the dCRY Trp chain has evolutionary importance for light sensing, and its manipulation has implications for optogenetic applications of CRYs.

Breast cancer has a multifactorial etiology. One of the supposed and novel mechanisms is an alteration of circadian gene expression. Circadian genes play a crucial role in many physiological processes. These processes, such as genomic stability, DNA repair mechanism and apoptosis, are frequently disrupted in breast tumors. To assess the significance of circadian gene expression in breast cancer, we carried out an analysis of CLOCK, BMAL1, NPAS2, PER1, PER2, PER3 and CRY1, CRY2, TIMELESS, CSNK1E expression by the use of the quantitative Real-Time PCR technique in tumor tissue and non-tumor adjacent normal tissue sampled from 107 women with a newly diagnosed disease. The obtained data were compared to the clinical and histopathological features. PER1, PER2, PER3, CRY2 were found to be significantly down-expressed, while CLOCK, TIMELESS were over-expressed in the studied tumor samples compared to the non-tumor samples. Only gene expression of CRY1 was significantly down-regulated with progression according to the TNM classification. We found significantly decreased expression of CRY2, PER1, PER2 genes in the ER/PR negative breast tumors compared to the ER/PR positive tumors. Additionally, expression of CRY2, NPAS2 genes had a decreased level in the poorly differentiated tumors in comparison with the well and moderately differentiated ones. Our results indicate that circadian gene expression is altered in breast cancer tissue, which confirms previous observations from various animal and in vitro studies.

Abstract Context Adrenal insufficiency (AI) requires lifelong glucocorticoid (GC) replacement. Conventional therapies do not mimic the endogenous cortisol circadian rhythm. Clock genes are essential components of the machinery controlling circadian functions and are influenced by GCs. However, clock gene expression has never been investigated in patients with AI. Objective To evaluate the effect of the timing of GC administration on circadian gene expression in peripheral blood mononuclear cells (PBMCs) of patients from the Dual Release Hydrocortisone vs Conventional Glucocorticoid Replacement in Hypocortisolism (DREAM) trial. Design Outcome assessor–blinded, randomized, active comparator clinical trial. Participants and Intervention Eighty-nine patients with AI were randomly assigned to continue their multiple daily GC doses or switch to an equivalent dose of once-daily modified-release hydrocortisone and were compared with 25 healthy controls; 65 patients with AI and 18 controls consented to gene expression analysis. Results Compared with healthy controls, 19 of the 68 genes were found modulated in patients with AI at baseline, 18 of which were restored to control levels 12 weeks after therapy was switched: ARNTL [BMAL] (P = 0.024), CLOCK (P = 0.016), AANAT (P = 0.021), CREB1 (P = 0.010), CREB3 (P = 0.037), MAT2A (P = 0.013); PRKAR1A, PRKAR2A, and PRKCB (all P < 0.010) and PER3, TIMELESS, CAMK2D, MAPK1, SP1, WEE1, CSNK1A1, ONP3, and PRF1 (all P < 0.001). Changes in WEE1, PRF1, and PER3 expression correlated with glycated hemoglobin, inflammatory monocytes, and CD16+ natural killer cells. Conclusions Patients with AI on standard therapy exhibit a dysregulation of circadian genes in PBMCs. The once-daily administration reconditions peripheral tissue gene expression to levels close to controls, paralleling the clinical outcomes of the DREAM trial (NCT02277587). We compared multiple-times-a-day vs once-daily modified-release hydrocortisone in adrenal insufficiency and found a significant effect on the expression of several clock-related genes.

The cell cycle is under circadian regulation. Oncogenes can dysregulate circadian-regulated genes to disrupt the cell cycle, promoting tumor cell proliferation. As a regulator of G2/M arrest in response to DNA damage, the circadian gene Timeless Circadian Clock (TIMELESS) coordinates this connection and is a potential locus for oncogenic manipulation. TIMELESS expression was evaluated using RNASeq data from TCGA and by RT-qPCR and western blot analysis in a panel of colon cancer cell lines. TIMELESS expression following ERK inhibition was examined via western blot. Cell metabolic capacity, propidium iodide, and CFSE staining were used to evaluate the effect of TIMELESS depletion on colon cancer cell survival and proliferation. Cell metabolic capacity following TIMELESS depletion in combination with Wee1 or CHK1 inhibition was assessed. TIMELESS is overexpressed in cancer and required for increased cancer cell proliferation. ERK activation promotes TIMELESS expression. TIMELESS depletion increases γH2AX, a marker of DNA damage, and triggers G2/M arrest via increased CHK1 and CDK1 phosphorylation. TIMELESS depletion in combination with Wee1 or CHK1 inhibition causes an additive decrease in cancer cell metabolic capacity with limited effects in non-transformed human colon epithelial cells. The data show that ERK activation contributes to the overexpression of TIMELESS in cancer. Depletion of TIMELESS increases γH2AX and causes G2/M arrest, limiting cell proliferation. These results demonstrate a role for TIMELESS in cancer and encourage further examination of the link between circadian rhythm dysregulation and cancer cell proliferation.

Daily temporal organisation offers a fitness advantage and is determined by an interplay between environmental rhythms and circadian clocks. While light:dark cycles robustly synchronise circadian clocks, it is not clear how animals experiencing only weak environmental cues deal with this problem. Like humans, Drosophila originate in sub-Saharan Africa and spread North up to the polar circle, experiencing long summer days or even constant light (LL). LL disrupts clock function, due to constant activation of CRYPTOCHROME, which induces degradation of the clock protein TIMELESS (TIM), but temperature cycles are able to overcome these deleterious effects of LL. We show here that for this to occur a recently evolved natural timeless allele ( ls-tim ) is required, encoding the less light-sensitive L-TIM in addition to S-TIM, the only form encoded by the ancient s-tim allele. We show that only ls-tim flies can synchronise their behaviour to semi-natural conditions typical for Northern European summers, suggesting that this functional gain is driving the Northward ls-tim spread. The genus Drosophila originate in subSaharan Africa and spread North up to the polar circle where they experience long days in the summer or even constant light. Here, the authors show that a form of the TIMELESS protein enables flies to synchronise their behavioural activity to long summer days

Background Accumulating evidence has suggested an oncogenic effect of diurnal disruption on cancer progression. To test whether targeting circadian rhythm by dietary strategy suppressed lung cancer progression, we adopted 6-h time-restricted feeding (TRF) paradigm to elucidate whether and how TRF impacts lung cancer progression. Methods This study used multiple lung cancer cell lines, two xenograft mouse models, and a chemical-treated mouse lung cancer model. Stable TIM-knockdown and TIM-overexpressing A549 cells were constructed. Cancer behaviors in vitro were determined by colony formation, EdU proliferation, wound healing, transwell migration, flow cytometer, and CCK8 assays. Immunofluorescence, pathology examinations, and targeted metabolomics were also used in tumor cells and tissues. mCherry-GFP-LC3 plasmid was used to detect autophagic flux. Results We found for the first time that compared to normal ad libitum feeding, 6-h TRF inhibited lung cancer progression and reprogrammed the rhythms of metabolites or genes involved in glycolysis and the circadian rhythm in tumors. After TRF intervention, only timeless (TIM) gene among five lung cancer-associated clock genes was found to consistently align rhythm of tumor cells to that of tumor tissues. Further, we demonstrated that the anti-tumor effect upon TRF was partially mediated by the rhythmic downregulation of the TIM and the subsequent activation of autophagy. Combining TRF with TIM inhibition further enhanced the anti-tumor effect, comparable to treatment efficacy of chemotherapy in xenograft model. Conclusions Six-hour TRF inhibits lung cancer progression and reshapes circadian metabolism, which is partially mediated by the rhythmic downregulation of the TIM and the subsequent upregulation of autophagy.

Background Breast cancer is the most common malignancy and the leading cause of cancer death among women. TIMELESS (TIM), a circadian rhythm regulator, has been recently implicated in the progression of human cancer. However, the role of TIM in the progression of breast cancer has not been well-characterized. Methods Immunohistochemistry (IHC) staining was used to examine TIM levels in breast cancer specimens. Mammosphere formation analysis and side population analysis were used to examine the effect of TIM on the self-renewal of breast cancer stem cells. A wound healing assay and a Transwell assay were used to determine the role of TIM in breast cancer cell migration and invasion. A soft agar growth assay in vitro and tumorigenicity in vivo were used to determine the role of TIM in tumorigenicity. Results TIM levels in both breast cancer cell lines and tissues were significantly upregulated. Patients with high TIM had poorer prognosis than patients with low TIM. Overexpression of TIM dramatically enhanced, while knockdown of TIM suppressed the self-renewal of cancer stem cells (CSCs), cell invasion and migration abilities of breast cancer cells in vitro. Moreover, overexpression of TIM significantly augmented, while knockdown of TIM reduced the tumorigenicity of breast cancer cells in vivo. Mechanism studies revealed that TIM upregulated the expression and the trans-activity of the well-known oncogene MYC. Inhibition of MYC significantly blocked the effects of TIM on CSC population, cell invasion and anchor-independent cell growth. Conclusion TIM plays an important role in promoting breast cancer progression and may represent a novel therapeutic target for breast cancer.

Transcription-translation feedback loops that comprise eukaryotic circadian clocks rely upon temporal delays that separate the phase of active transcription of clock genes, such as Drosophila period (per) and timeless (tim), from negative feedback by the two proteins. However, our understanding of the mechanisms involved is incomplete. Through an RNA interference screen, we found that pre-mRNA processing 4 (PRP4) kinase, a component of the U4/U5.U6 triple small nuclear ribonucleoprotein (tri-snRNP) spliceosome, and other tri-snRNP components regulate cycling of the molecular clock as well as rest:activity rhythms. Unbiased RNA-Sequencing uncovered an alternatively spliced intron in tim whose increased retention upon prp4 downregulation leads to decreased TIM levels. We demonstrate that the splicing of tim is rhythmic with a phase that parallels delayed accumulation of the protein in a 24 hr cycle. We propose that alternative splicing constitutes an important clock mechanism for delaying the daily accumulation of clock proteins, and thereby negative feedback by them. Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter ).