Biology subjects

Diernfellner, A. C. R.

Publications and source records attributed to Diernfellner, A. C. R..

5 recordsLinked to original sources

bioRxiv2023

CK1δ homeostasis by activity-dependent shuttling and degradation of orphan kinase

Casein kinase 1{delta} (CK1{delta}) is a simple monomeric enzyme involved in the regulation of a variety of functions, including signal transduction, the circadian clock, and the cell cycle. Although CK1{delta} is targeted by the ubiquitin ligase APC/CCdh1 is not understood how CK1{delta} expression is regulated to support its multiple functions. Here, we show that kinase activity controls CK1{delta} homeostasis by coordinating two competing processes: export from the nucleus to ensure distribution of CK1{delta} between its assembly partners, and proteasomal degradation of unassembled CK1{delta} in the nucleus to keep the amount of active, potentially deleterious orphan kinase low. During mitosis, CK1{delta} is released from centrosomes and stabilized by (auto)phosphorylation to preserve it for the subsequent G1 phase. TeaserCompetitive nuclear export and nuclear degradation of active CK1{delta} ensure efficient partner interaction and keep unassembled kinase levels low.

biochemistry↗

bioRxiv2023

Transcription activator WCC recruits deacetylase HDA3 to control transcription dynamics and bursting in Neurospora

RNA polymerase II initiates transcription either randomly or in bursts. We examined the light-dependent transcriptional activator White Collar Complex (WCC) of Neurospora to characterize the transcriptional dynamics of the strong vivid (vvd) promoter and the weaker frequency (frq) promoter. We show that WCC is not only an activator but also represses transcription by recruiting histone deacetylase 3 (HDA3). Our data suggest that bursts of frq transcription are governed by a long-lived refractory state established and maintained by WCC and HDA3 at the core promoter, whereas transcription of vvd is determined by WCC binding dynamics at an upstream activating sequence. Thus, in addition to stochastic binding of transcription factors, transcription factor-mediated repression may also influence transcriptional bursting. TEASERBalanced interaction of transcription factor with coactivator and corepressors determines transcription dynamics and bursting.

molecular biology↗

bioRxiv2022

Antisense transcription of the Neurospora frequency gene is rhythmically regulated by CSP-1 repressor but dispensable for clock function

The circadian clock of Neurospora crassa is based on a negative transcriptional/translational feedback loops. The frequency (frq) gene controls the morning-specific rhythmic transcription of a sense RNA encoding FRQ, the negative element of the core circadian feedback loop. In addition, a long noncoding antisense RNA, qrf, is rhythmically transcribed in an evening-specific manner. It has been reported that the qrf rhythm relies on transcriptional interference with frq transcription and that complete suppression of qrf transcription impairs the circadian clock. We show here that qrf transcription is dispensable for circadian clock function. Rather, the eveningspecific transcriptional rhythm of qrf is mediated by the morning-specific repressor CSP-1. Since CSP-1 expression is induced by light and glucose, this suggests a rhythmic coordination of qrf transcription with metabolism. However, a possible physiological significance for the circadian clock remains unclear, as suitable assays are not available.

molecular biology↗

bioRxiv2022

Adaptation to starvation requires a flexible circadian clockwork in Neurospora crassa

The circadian clock governs rhythmic cellular functions by driving expression of a substantial fraction of the genome and thereby significantly contributes to the adaptation to changing environmental conditions. Using the circadian model organism Neurospora crassa, we show that molecular timekeeping is robust even under severe limitation of carbon sources, however, stoichiometry, phosphorylation and subcellular distribution of the key clock components display drastic alterations. Protein kinase A, protein phosphatase 2A and glycogen synthase kinase are involved in the molecular reorganization of the clock. RNA-seq analysis reveals that the transcriptomic response of metabolism to starvation is highly dependent on the positive clock component WC-1. Moreover, our molecular and phenotypic data indicate that a functional clock facilitates recovery from starvation. We suggest that the molecular clock is a flexible network that allows the organism to maintain a rhythmic physiology and preserve fitness even under long-term nutritional stress.

cell biology↗

bioRxiv2022

Data-driven modelling captures dynamics of the circadian clock ofNeurospora crassa

Eukaryotic circadian clocks are based on self-sustaining, cell-autonomous oscillatory feedback loops that can synchronize with the environment via recurrent stimuli (zeitgebers) such as light. The components of biological clocks and their network interactions are becoming increasingly known, calling for a quantitative understanding of their role for clock function. However, the development of data-driven mathematical clock models has remained limited by the lack of sufficiently accurate data. Here we present a comprehensive model of the circadian clock of Neurospora crassa that describe free-running oscillations in constant darkness and entrainment in light-dark cycles. To parameterize the model, we measured high-resolution time courses of luciferase reporters of morning and evening specific clock genes in WT and a mutant strain. Fitting the model to such comprehensive data allowed estimating parameters governing circadian phase, period length and amplitude, and the response of genes to light cues. Our model suggests that functional maturation of the core clock protein Frequency (FRQ) causes a delay in negative feedback that is critical for generating circadian rhythms.

systems biology↗