Biology subjects

Pospisek, M.

Publications and source records attributed to Pospisek, M..

4 recordsLinked to original sources

bioRxiv2020

p38-MAPK mediated rRNA processing and translation regulation enables PrE differentiation during mouse blastocyst maturation.

Backgroundp38-MAPKs are stress-activated kinases necessary for placental development and nutrient and oxygen transfer during murine post-implantation development. In preimplantation development, p38-MAPK activity is required for blastocyst formation. Additionally, we have previously reported its role in regulating specification of inner cell mass (ICM) towards primitive endoderm (PrE), although a comprehensive mechanistic understanding is currently limited. Adopting live embryo imaging, proteomic and transcriptomic approaches, we report experimental data that directly address this deficit. ResultsChemical inhibition of p38-MAPK activity during blastocyst maturation causes impaired blastocyst cavity expansion, most evident between the third and tenth hours post inhibition onset. We identify an overlapping minimal early blastocyst maturation window of p38-MAPKi inhibition (p38-MAPKi) sensitivity, that is sufficient to impair PrE cell fate by the late blastocyst (E4.5) stage. Comparative proteomic analyses reveal substantial downregulation of ribosomal proteins, the mRNA transcripts of which are also significantly upregulated. Ontological analysis of the differentially expressed transcriptome during this developmental period reveals "translation" related gene transcripts as being most significantly, yet transiently, affected by p38-MAPKi. Moreover, combined assays consistently report concomitant reductions in de novo translation that are associated with accumulation of unprocessed rRNA precursors. Using a phosphoproteomic approach, {+/-} p38-MAPKi, we identified Mybpp1a, an rRNA transcription and processing regulator gene, as a potential p38-MAPK effector. We report that siRNA mediated clonal knockdown of Mybpp1a is associated with significantly diminished PrE contribution. Lastly, we show that defective PrE specification caused by p38-MAPKi (but not MEK/ERK signalling inhibition) can be partially rescued by activating the archetypal mTOR mediated translation regulatory pathway. ConclusionsActivated p38-MAPK controls blastocyst maturation in an early and distinctly transient developmental window by regulating gene functionalities related to translation, that creates a permissive environment for appropriate specification of ICM cell fate.

developmental biology↗

bioRxiv2020

Transcripts of vaccinia virus postreplicative genes do not contain a 5' methylguanosine cap

Vaccinia virus (VACV) is a prototypical poxvirus originally used for eradication of smallpox. Investigation into VACV mRNAs carried out almost half a century ago substantially contributed to the fundamental discovery of the 5 mRNA cap, a hallmark of all eukaryotic and many viral mRNAs. VACV research also facilitated the identification and understanding of the general mechanism of 5 mRNA cap synthesis. We characterized the VACV transcripts at the individual mRNA molecule level and found that vaccinia postreplicative mRNAs, containing nontemplated 5 poly(A) leaders, surprisingly lack the 5 cap structure in vivo. We also show that the lengths of the nontemplated leaders and the presence or absence of cap structures at the 5 mRNA ends are controlled by the initiator sequence of the VACV postreplicative promoters. One Sentence SummaryThe promoter sequence determines the synthesis of the 5 cap and poly(A) leaders in vaccinia virus postreplicative mRNAs.

molecular biology↗

bioRxiv2018

Messenger RNAs transcribed from yeast linear cytoplasmic plasmids possess unconventional 5’ and 3’ UTRs and suggest a novel mechanism of translation

Linear plasmids with almost identical compact genetic organization have been found in the cytoplasm of yeast species from nine genera. We employed pGKL1,2 plasmids from Kluyveromyces lactis as a model to investigate the previously unstudied transcriptome of yeast cytoplasmic linear plasmids. We performed 5 and 3 RACE analysis of all the pGKL1,2 mRNAs and found them not 3 polyadenylated and containing mostly uncapped 5 poly(A) leaders that are not complementary to the plasmid DNA. The degree of 5 capping and/or 5 polyadenylation is specific to each gene and is controlled by the corresponding promoter regions. We refined the description of the pGKL1,2 promoters and found new alternative promoters of several genes. We also provide evidence that K2ORF3 encodes an mRNA cap guanine-N7-methyltransferase and that 5 capped pGKL1,2 transcripts contain N7-methylated caps. Translation of pGKL1,2 transcripts is enhanced in Ism1{Delta} and pab1{Delta} strains and is independent of eIF4E and Pab1 translation factors. We suggested a model of a primitive regulation of pGKL1,2 plasmids gene expression where degree of 5 mRNA capping, degree of 5 non-template polyadenylation and presence of negative regulators as PAB1 and Lsm1 play an important role. Our data also suggest a close relationship between linear plasmids and poxviruses.

molecular biology↗

bioRxiv2018

Transcription apparatus of the yeast killer DNA plasmids: Architecture, function, and evolutionary origin

Transcription of extrachromosomal elements such as organelles, viruses, and plasmids is dependent on cellular RNA polymerase (RNAP) or intrinsic RNAP encoded by these elements. The yeast Kluyveromyces lactis contains killer DNA plasmids that bear putative non-canonical RNAP genes. Here, we describe the architecture and evolutionary origin of this transcription machinery. We show that the two RNAP subunits interact in vivo, and this complex interacts with another two plasmid-encoded proteins - the mRNA capping enzyme, and a putative helicase which interacts with plasmid-specific DNA. Further, we identify a promoter element that causes 5 polyadenylation of plasmid-specific transcripts via RNAP slippage during transcription initiation, and structural elements that precede the termination sites. As a result, we present a first model of the yeast killer plasmid transcription initiation and intrinsic termination. Finally, we demonstrate that plasmid RNAP and its promoters display high similarity to poxviral RNAP and promoters of early poxviral genes, respectively.

molecular biology↗