Gsα^(R201C)and estrogen reveal different subsets of bone marrow adiponectin expressing osteogenic cells

The Gsα/cAMP signaling pathway mediates the effect of a variety of hormones and factors that regulate the homeostasis of the post-natal skeleton.Hence,the dysregulated activity of Gsαdue to gain-of-function mutations (R201C/R201H)results in severe architectural and functional derangements of the entire bone/bone marrow organ.While the consequences of gain-of-function mutations of Gsαhave been extensively investigated in osteoblasts and in bone marrow osteoprogenitor cells at various differentiation stages,their effect in adipogenically-committed bone marrow stromal cells has remained unaddressed.We generated a mouse model with expression of Gsα^(R201C) driven by the Adiponectin(Adq)promoter.Adq-Gsα^(R201C) mice developed a complex combination of metaphyseal,diaphyseal and cortical bone changes.In the metaphysis,Gsα^(R201C) caused an early phase of bone resorption followed by bone deposition.Metaphyseal bone formation was sustained by cells that were traced by Adq-Cre and eventually resulted in a high trabecular bone mass phenotype.In the diaphysis,Gsα^(R201C),in combination with estrogen,triggered the osteogenic activity of Adq-Cre-targeted perivascular bone marrow stromal cells leading to intramedullary bone formation.Finally,consistent with the previously unnoticed presence of Adq-Cre-marked pericytes in intraosseous blood vessels,Gsα^(R201C) caused the development of a lytic phenotype that affected both cortical(increased porosity)and trabecular(tunneling resorption)bone.These results provide the first evidence that the Adq-cell network in the skeleton not only regulates bone resorption but also contributes to bone formation,and that the Gsα/cAMP pathway is a major modulator of both functions.

Challenges and perspectives for structural biology of IncRNAs-the example of the Xist IncRNA A-repeats

Following the discovery of numerous long non-coding RNA(IncRNA)transcripts in the human genome,their important roles in biology and human disease are emerging.Recent progress in experimental methods has enabled the identification of structural features of IncRNAs.However,determining high-resolution structures is challenging as IncRNAs are expected to be dynamic and adopt multiple conformations,which may be modulated by interaction with protein binding partners.The X-inactive specific transcript(Xist)is necessary for X inactivation during dosage compensation in female placental mammals and one of the beststudied IncRNAs.Recent progress has provided new insights into the domain organization,molecular features,and RNA binding proteins that interact with distinct regions of Xist.The A-repeats located at the 5'end of the transcript are of particular interest as they are essential for mediating silencing ofthe inactive X chromosome.Here,we discuss recent progress with elucidating structural features of the Xist IncRNA,focusing on the A-repeats.We discuss the experimental and computational approaches employed that have led to distinct structural models,likely reflecting the intrinsic dynamics of this RNA.The presence of multiple dynamic conformations may also play an important role in the formation ofthe associated RNPs,thus influencing the molecular mechanism underlying the biological function of the Xist A-repeats.We propose that integrative approaches that combine biochemical experiments and high-resolution structural biology in vitro with chemical probing and functional studies in vivo are required to unravel the molecular mechanisms of IncRNAs.

Transcriptional Regulation of the Ambient Temperature Response by H2A.Z Nucleosomes and HSF1 Transcription Factors in Arabidopsis

Temperature influences the distribution, range, and phenology of plants. The key transcriptional activators of heat shock response in eukaryotes, the heat shock factors （HSFs）, have undergone large-scale gene amplification in plants. While HSFs are central in heat stress responses, their role in the response to ambient temperature changes is less well understood. We show here that the warm ambient temperature transcriptome is dependent upon the HSFA1 clade ofArabidopsis HSFs, which cause a rapid and dynamic eviction of H2A.Z nucleosomes at target genes. A transcriptional cascade results in the activation of multiple downstream stress-responsive transcription factors, triggering large-scale changes to the transcriptome in response to elevated temperature. H2A.Z nucleosomes are enriched at temperature-responsive genes at non-inducible temperature, and thus likely confer inducibility of gene expression and higher responsive dynamics. We propose that the antagonistic effects of H2A.Z and HSF1 provide a mechanism to activate gene expression rapidly and precisely in response to temperature, while preventing leaky transcription in the absence of an activation signal.

Peptide asparaginyl ligases——renegade peptide bond makers

Making peptide bonds is tightly controlled by genetic code and machinery which includes cofactors,ATP,and RNAs.In this regard,the stand-alone and genetic-code-independent peptide ligases constitute a new family of renegade peptide-bond makers.A prime example is butelase-1,an Asn/Asp(Asx)-specific ligase that structurally belongs to the asparaginyl endopeptidase family.Butelase-1 specifically recognizes a C-terminal Asx-containing tripeptide motif,Asn/Asp-Xaa-Yaa(Xaa and Yaa are any amino acids),to form a site-specific Asn-Xaa peptide bond either intramolecularly as cyclic proteins or intermolecularly as modified proteins.Our work in the past five years has validated that butelase-1 is a potent and versatile ligase.Here we review the advances in ligases,with a focus on butelase-1,and their applications in engineering bioactive peptides and precision protein modifications,antibody-drug conjugates,and live-cell labeling.

The conserved ubiquitin-like protein Hub1 plays a critical role in splicing in human cells

Different from canonical ubiquitin-like proteins, Hub1 does not form covalent conjugates with substrates but binds proteins noncovalently. In Socchoromyces cerevisioe, Hub1 associates with spUceosomes and mediates alternative splicing of SRCI, without affecting pre-mRNA splicing generaity. Human Hub1 is highty similar to its yeast homotog, but its cellular function remains largely unexplored. Here, we show that human Hub1 binds to the spliceosomal protein Snu66 as in yeast; however, unlike its 5. cerevisioe homolos, human Hub1 is essential for viability. Prolonged in vivo depletion of human Hub1 leads to various cellular defects, including splicing speckle abnormalities, partial nuclear retention of mRNAs, mitotic catastrophe, and consequently cell death by apoptosis. Early consequences of Hub1 depletion are severe splicing defects, however, only for specific splice sites leading to exon skipping and intron retention. Thus, the ubiquitin-iike protein Hub1 is not a canonlcal spliceosomal factor needed generally for splicing, but rather a modulator of spliceosome performance and facilitator of alternative splicing.

Vaccination versus SARS-CoV-2 Omicron:three vaccine doses win the battle

The here highlighted study by Garcia-Beltran et al.demonstrates that SARS-CoV-2 Omicron can largely escape the immune responses.Hence,while two doses of COVID-19 vaccines seem to be insufficient to provide protection against Omicron,a third dose provides mature neutralizing antibodies to enhance the response.1 Since March 2020,when the World Health Organization(WHO;www.who.int)officially declared the COVID-19 pandemic caused by the SARS-CoV-2.