Cryptochromes

A circadian clock protein cryptochrome inhibits the expression of inflammatory cytokines in Chinese mitten crab (Eriocheir sinensis)

Cryptochrome (Cry), as important flavoprotein, plays a key role in regulating the innate immune response, such as the release of inflammatory cytokines. In the present study, a cryptochrome homologue (EsCry) was identified from Chinese mitten crab Eriocheir sinensis, which contained a typical DNA photolyase domain, a FAD binding domain. The transcripts of EsCry were highly expressed at 11:00, and lowest at 3:00 within one day, while those of Interleukin enhancer binding factor (EsILF), Lipopolysaccharide-induced TNF-alpha factor (EsLITAF), Tumor necrosis factor (EsTNF) and Interleukin-16 (EsIL-16) showed a rhythm expression pattern contrary to EsCry. After EsCry was knocked down by dsEsCry injection, mRNA transcripts of Timeless (EsTim), Cycle (EsCyc), Circadian locomotor output cycles kaput (EsClock), Period (EsPer), and EsLITAF, EsTNF, EsILF, EsIL-16, as well as phosphorylation level of Dorsal significantly up-regulated. The transcripts of EsLITAF, EsTNF, EsILF, and EsIL-16 in EsCry-RNAi crabs significantly down-regulated after injection of NF-κB inhibitor. The interactions of EsCyc and EsCry, EsCyc and Dorsal were observed in vitro. These results indicated that EsCry negatively regulated the expression of the cytokine TNF and IL-16 via inhibiting their transcription factor LITAF and ILF through NF-κB signaling pathway, which provide evidences to better understand the circadian regulation mechanism of cytokine production in crabs.

Vertebrate ancient opsin and melanopsin: divergent irradiance detectors

Both vertebrates and invertebrates respond to light by utilising a wide-ranging array of photosensory systems, with diverse photoreceptor organs expressing a characteristic photopigment, itself consisting of an opsin apoprotein linked to a light-sensitive retinoid chromophore based on vitamin A. In the eye, the pigments expressed in both cone and rod photoreceptors have been studied in great depth and mediate contrast perception, measurement of the spectral composition of environmental light, and thus classical image forming vision. By contrast, the molecular basis for non-visual and extraocular photoreception is far less understood; however, two photopigment genes have become the focus of much study, the vertebrate ancient (va) opsin and melanopsin (opn4). In this review, we discuss the history of discovery for each gene, as well as focusing on the evolution, expression profile, functional role and broader physiological significance of each photopigment. Recently, it has been suggested independently by Arendt et al. and Lamb that an ancestral opsin bifurcated in early metazoans and evolved into two quite different photopigments, one expressed in rhabdomeric photoreceptors and the other in ciliary photoreceptors. This interpretation of the evolution of the metazoan eye has provided a powerful framework for understanding photobiological organization. Their proposal, however, does not encompass all current experimental observations that would be consistent with what we term a central "Evolution of Photosensory Opsins with Common Heredity (EPOCH)" hypothesis to explain the complexity of animal photosensory systems. Clearly, many opsin genes (e.g. va opsin) simply do not fit neatly within this scheme. Thus, the review concludes with a discussion of these anomalies and their context regarding the phylogeny of photoreceptor and photopigment development.

Cycling of CRYPTOCHROME proteins is not necessary for circadian-clock function in mammalian fibroblasts

BACKGROUND

An interlocked transcriptional-translational feedback loop (TTFL) is thought to generate the mammalian circadian clockwork in both the central pacemaker residing in the hypothalamic suprachiasmatic nuclei and in peripheral tissues. The core circadian genes, including Period1 and Period2 (Per1 and Per2), Cryptochrome1 and Cryptochrome2 (Cry1 and Cry2), Bmal1, and Clock are indispensable components of this biological clockwork. The cycling of the PER and CRY clock proteins has been thought to be necessary to keep the mammalian clock ticking.

RESULTS

We provide a novel cell-permeant protein approach for manipulating cryptochrome protein levels to evaluate the current transcription and translation feedback model of the circadian clockwork. Cell-permeant cryptochrome proteins appear to be functional on the basis of several criteria, including the abilities to (1) rescue circadian properties in Cry1(-/-)Cry2(-/-) mouse fibroblasts, (2) act as transcriptional repressors, and (3) phase shift the circadian oscillator in Rat-1 fibroblasts. By using cell-permeant cryptochrome proteins, we demonstrate that cycling of CRY1, CRY2, and BMAL1 is not necessary for circadian-clock function in fibroblasts.

CONCLUSIONS

These results are not supportive of the current version of the transcription and translation feedback-loop model of the mammalian clock mechanism, in which cycling of the essential clock proteins CRY1 and CRY2 is thought to be necessary.

Histone acetyltransferase complexes: one size doesn't fit all

Over the past 10 years, the study of histone acetyltransferases (HATs) has advanced significantly, and a number of HATs have been isolated from various organisms. It emerged that HATs are highly diverse and generally contain multiple subunits. The functions of the catalytic subunit depend largely on the context of the other subunits in the complex. We are just beginning to understand the specialized roles of HAT complexes in chromosome decondensation, DNA-damage repair and the modification of non-histone substrates, as well as their role in the broader epigenetic landscape, including the role of protein domains within HAT complexes and the dynamic interplay between HAT complexes and existing histone modifications.