NEW CONTROL MECHANISMS OF CELLULAR CYCLE REGULATORS

Characterisation of Start Whi7 repressor.

Our group has characterised a new regulator by importing in the Start Whi7 transition. Whi7 serves as a transcriptional repressor of the Start programme in collaboration with Whi5 in that function, so as in mammals with the Rb family, the control of the cell cycle initiation depends on the competition between different repressors. The group works seek to advance in the characterisation of Whi7 regulation and function and the comparison with Whi5 in different physiological conditions. It will help us understand how the action of different repressors in the cycle start control coordination. We also investigate the relation between Whi7 and the route of protein kinase C. The fact that a member of the Rb family mutates in almost all the tumours reinforces the importance of studying the role of these G1 repressors.

New control mechanisms and other cell cycle regulators.

Other group works revolve around the mechanisms of spatial regulation in the cell cycle control, mechanisms that imply control on subcellular location of key proteins on the cycle progression. We have particularly studied the role of karyopherin Msn5 in transcription factor control (Swi6, Swi4, Mbp1, Swi5, Whi5) and Start cyclettes (Cln1, Cln2). We also research functional specificity determinants of cyclines and the identification of new mechanism to control cyclines synthesis and degradation (Cln2, Clb2).

PKC BY DNA INTEGRITY CHECKPOINT REGULATION

Using yeast as a model, our group has introduced a new player in the genotoxic stress response: protein kinase C (PKC). We had previously described genetic and functional interactions linking PKC to the S-stage cyclin Clb5, revealing a functional overlap with a new morphogenetic function for Clb5 and a new function related to genomic integrity for the PKC pathway. Subsequently, we have described the essential role that the MAPK kinase Slt2 of the PKC pathway plays in the response to genotoxic stress. More recently, we have shown that yeast Pkc1 activity is essential for the activation of the DNA integrity checkpoint in response to numerous genotoxic treatments. More recently, we have shown that yeast Pkc1 activity is essential for activation of the DNA integrity checkpoint in response to numerous genotoxic treatments. Important cellular mechanisms are evolutionarily conserved from yeast to humans. This is especially remarkable in the field of cell cycle and DNA integrity checkpoint. Thus, the mammalian PKCδ isoform is able to restore the function of the DNA integrity checkpoint when expressed in yeast cells by mutating pkc1. Checkpoint function is also impaired in he-la cells when PKcδ is inhibited. All the results indicate that PKCδ would therefore have an important role in the control of the checkpoint in mammalian cells. This relationship is of great importance since the correct functioning of the checkpoint is essential to prevent cancer. In fact, PKCδ has been linked to tumour development. The group's work aims to advance our understanding of the molecular clues to the role of PKC in the control of genomic integrity by means of a parallel study in yeast and mammalian cells.

Yeast cells study

Since the PKC by DNA integrity checkpoint control mechanism is preserved, Pkc1 study on yeast can give important keys about PKCδ function. Concretely, we research on how Pkc1 activates the checkpoint by identifying waste and domains important to its function. We also research on new mechanisms for MAPK Slt of te PKC route take part in the cell response to genotoxic stress.

On the other hand, the study in simpler organisms such as yeast can contribute to the understanding of the functions carried out by a protein in more complex systems. This is particularly true in the case of protein families such as PKCs, since it allows studies to be carried out with one of the isoforms in the absence of the others. Therefore, in parallel to the work with Pkc1, we are studying how PKCδ controls the DNA integrity checkpoint in yeast. The study with PKCδ is completed with the design of a bioassay in yeast that allows us to study the effect of compounds of interest on PKCδ activity in a simpler and cheaper way and, above all, without interference from the other PKC isoforms present in mammalian cells.

Mammal cells study

Our results say that PKCδ has a crucial role in the checkpoint control in mammal cells. We also research on the response to cellular damage in primary cell, embryo stem cells and neural stem cells particularly due to the relevance of the genomic integrity maintenance in cells with high proliferation ability like stem cells ad their role in cancer.

IMPLICATIONS IN CANCER: PKCδ AND SKIN CARCINOMA OF SQUAMOUS CELLS

The proper working of the DNA integrity checkpoint is crucial for the cell viability in order to prevent illnesses like cancer. Our results point out that PKCδ plays a role on the checkpoint activation, so it is not strange that PKCδ is related to tumour growth. As an extension of basic research work on PKCδ to uncover more of its relation with cancer, a systematic analysis of PKCδ activity and the genomic stability in different stages of skin carcinoma of squamous cells is being carried out. Skin carcinoma of squamous cells is the type of cancer which PKCδ activity has been related to. PKCδ controls epigenetic modifications and due to the connection between epigenetics and cancer, there will be a study on epigenome through the different stages of skin carcinoma of squamous cells (cSCC). In order to further research on skin carcinoma evolution, the study of miRNA profiles, the differential expression PKCδ regulation in tumour cells could be relted to, will be necessary. The goal is to provide a mechanism interpretation at a molecular level of Cscc EVOLUTION.