Importance of molecular cell biology investigations in human medicine in the story of the Hutchinson-Gilford progeria syndrome

Ranged among laminopathies, Hutchinson–Gilford progeria syndrome is a syndrome that involves premature aging, leading usually to death at the age between 10 to 14 years predominatly due to a myocardial infarction or a stroke. In the lecture I shall overview the importance of molecular cell biology investigations that led to the discovery of the basic mechanism standing behind this rare syndrome. The genetic basis in most cases is a mutation at the nucleotide position 1824 of the lamin A gene. At this position, cytosine is substituted for thymine so that a cryptic splice site within the precursor mRNA for lamin A is generated. This results in a production of abnormal lamin A, termed progerin, its presence in cells having a deleterious dominant effect. Depending on the cell type and tissue, progerin induces a pleiotropy of defects that vary in different tissues. The present endeavour how to challenge this terrible disease will be also mentioned

Nucleologenesis in the Caenorhabditis elegans Embryo

In the Caenorhabditis elegans nematode, the oocyte nucleolus disappears prior to fertilization. We have now investigated the re-formation of the nucleolus in the early embryo of this model organism by immunostaining for fibrillarin and DAO-5, a putative NOLC1/Nopp140 homolog involved in ribosome assembly. We find that labeled nucleoli first appear in somatic cells at around the 8-cell stage, at a time when transcription of the embryonic genome begins. Quantitative analysis of radial positioning showed the nucleolus to be localized at the nuclear periphery in a majority of early embryonic nuclei. At the ultrastructural level, the embryonic nucleolus appears to be composed of a relatively homogenous core surrounded by a crescent-shaped granular structure. Prior to embryonic genome activation, fibrillarin and DAO-5 staining is seen in numerous small nucleoplasmic foci. This staining pattern persists in the germline up to the ∼100-cell stage, until the P4 germ cell divides to give rise to the Z2/Z3 primordial germ cells and embryonic transcription is activated in this lineage. In the ncl-1 mutant, which is characterized by increased transcription of rDNA, DAO-5-labeled nucleoli are already present at the 2-cell stage. Our results suggest a link between the activation of transcription and the initial formation of nucleoli in the C. elegans embryo

Retionidy regulovaná transkripce genu a protinádorová aktivita retinoidům podobných molekul

Nuclear Retinoic Acid (RA) Receptors (RARs) activate gene expression through dynamic interactions with coregulators in coordination with the ligand and phosphorylation processes. In the first part of this work, we showed that during RA-dependent activation of the RARq isotype, the pi 60 coactivator pCIP/ACTR/AIВ-1 /RAC-3/TRAM-1 /SRC-3 was phosphorylated by p38MAPK. SRC-3 phosphorylation was correlated to an initial facilitation of RARa-target genes activation, via the control of the dynamics of the interactions of the coactivator with RARa. Then phosphorylation inhibited transcription via promoting the degradation of SRC-3. In line with this, inhibition of p38MAPK markedly enhanced RARa-mediated transcription and RA-dependent induction of cell differentiation. SRC-3 phosphorylation and degradation occurred only within the context of RARa complexes, suggesting that the RAR isotype defined a phosphorylation code through dictating the accessibility of the coactivator to p38MAPK. We proposed a model in which RARa transcriptional activity was regulated by SRC-3 through coordinated events that are fine- tuned by RA and p38MAPK. The retinoid related molecules (RRMs), ST1926 and CD437, are promising anti-cancer agents. In the second part of this work, we compared the RAR trans-activating properties of the two RRMs...3rd Medical Department - Clinical Department of Endocrinology and MetabolismIII. interní klinika - klinika endokrinologie a metabolismu 1.LF a VFN v PrazeFirst Faculty of Medicine1. lékařská fakult

Retinoid regulation of target gene transcription and antitumor activity of retinoid related molecules

Nuclear Retinoic Acid (RA) Receptors (RARs) activate gene expression through dynamic interactions with coregulators in coordination with the ligand and phosphorylation processes. In the first part of this work, we showed that during RA-dependent activation of the RARq isotype, the pi 60 coactivator pCIP/ACTR/AIВ-1 /RAC-3/TRAM-1 /SRC-3 was phosphorylated by p38MAPK. SRC-3 phosphorylation was correlated to an initial facilitation of RARa-target genes activation, via the control of the dynamics of the interactions of the coactivator with RARa. Then phosphorylation inhibited transcription via promoting the degradation of SRC-3. In line with this, inhibition of p38MAPK markedly enhanced RARa-mediated transcription and RA-dependent induction of cell differentiation. SRC-3 phosphorylation and degradation occurred only within the context of RARa complexes, suggesting that the RAR isotype defined a phosphorylation code through dictating the accessibility of the coactivator to p38MAPK. We proposed a model in which RARa transcriptional activity was regulated by SRC-3 through coordinated events that are fine- tuned by RA and p38MAPK. The retinoid related molecules (RRMs), ST1926 and CD437, are promising anti-cancer agents. In the second part of this work, we compared the RAR trans-activating properties of the two RRMs..

Organization of human replicon: Singles or zipping couples?

According to a general paradigm, proper DNA duplication from each replication origin is ensured by two protein complexes termed replisomes. In prokaryotes and in budding yeast Saccharomyces cerevisiae, these two replisomes seem to be associated with one another until DNA replication initiated from the origin has finished. This arrangement results in the formation of the loop of newly synthesized DNA. However, arrangement of replisomes in other eukaryotic organisms including vertebrate cells is largely unknown. Here, we used in vivo labeling of DNA segments in combination with the electron microscopy tomography to describe the organization of replisomes in human HeLa cells. The experiments were devised in order to distinguish between a model of independent replisomes and a model of replisome couples. The comparative analysis of short segments of replicons labeled in pulse-chase experiments of various length shows that replisomes in HeLa cells are organized into the couples during DNA replication. Moreover, our data enabled to suggest a new model of the organization of replicated DNA. According to this model, replisome couples produce loop with the associated arms in the form of four tightly associated 30 nm fibers