El consumidor vulnerable de base de coca

Principal Investigator:

Lea Sistonen, Ph.D., Professor of Cell and Molecular Biology, Department of Biosciences, Åbo Akademi University. Laboratory address: Centre for Biotechnology, BioCity, Tykistökatu 6,

P.O.BOX 123, FI-20521 Turku, Finland.

Tel. +358-2-333 8028, 215 3311; Fax +358-2-333 8000; Email: [email protected], [email protected]

Biography:

Lea Sistonen (b. 1959) completed her undergraduate studies at Åbo Akademi University in 1984 and received her Ph.D. from the University of Helsinki in 1990. She was a post-doctoral fellow at Northwestern University in Dr. Richard I. Morimoto’s laboratory in 1990-1993 (Fogarty International Fellowship 1991-1993). In November 1993 she joined the Centre for Biotechnology as a senior research fellow in molecular biology. In April 2000 she was appointed as Professor of Cell and Molecular Biology at Åbo Akademi University. During the 5-year period 2004-2009 she was Academy Professor, the Academy of Finland.

Personnel:

Post-doctoral fellows: Julius Anckar, Ph.D., Eva Henriksson, Ph.D., Malin Åkerfelt, Ph.D.

Graduate students: Johanna Ahlskog, M.Sc., Johanna Björk, M.Sc., Henri Blomster, M.Sc., Zhanna Chitikova, M.Sc., Alexandra Elsing, M.Sc., Anton Sandqvist, M.Sc., Anniina Vihervaara, M.Sc. Technician: Helena Saarento, M.Sc.

Undergraduate students: Anna Aalto, Heidi Bergman, Malin Blom, Marek Budzynski, Henrica Karlberg, Karoliina Rautoma, Jenny Siimes, Aki Vartiainen

Description of the Project:

The heat shock response is an evolutionarily well-conserved cellular defence mechanism against protein-damaging stresses, such as elevated temperatures or hyperthermia, heavy metals, and viral and bacterial infections. The heat shock proteins (Hsps) function as molecular chaperones to protect cells by binding to partially denatured proteins, dissociating protein aggregates, and regulating the correct folding and intracellular translocation of newly synthesized polypeptides. Hsps are transcriptionally regulated by heat shock factors, HSFs. The mammalian HSF family consists of four members HSF1-4. Although HSFs are best known as inducible transcriptional regulators of genes encoding molecular chaperones and other stress proteins, they are also important for normal developmental processes and longevity pathways. The repertoire of HSF targets has recently expanded well beyond the heat shock genes, and the known functions governed by HSFs span from the heat shock response to development, metabolism, lifespan and disease, especially cancer and neurodegenerative disorders. Our main interest is in elucidating the molecular mechanisms by which the different members of the HSF family are regulated during normal development and under stressful conditions. In particular, we investigate both the expression and activity of HSF1 and HSF2. We have found that HSF1 is ubiquitously expressed and its activity is primarily regulated by various post-translational modifications

(PTMs), such as acetylation, phosphorylation and sumoylation. All these PTMs are induced by stress stimuli but their effects on HSF1 vary. While examining the multi-site phosphorylation of HSF1, we observed that in response to stress, HSF1 undergoes phosphorylation-dependent sumoylation within a bipartite motif which we found in many transcription factors and co-factors and gave name PDSM (phosphorylation-dependent sumoylation motif. Stress-inducible hyperphosphorylation and sumoylation of HSF1 occur very rapidly, whereas acetylation of HSF1 increases gradually, indicating a role for acetylation in the attenuation phase of the HSF1 activity cycle. Indeed, we have shown that among multiple lysine residues targeted by acetylation, K80 is located within the DNA-binding domain of HSF1 and its acetylation is required for reducing HSF1 DNA-binding activity. Moreover, the duration of HSF1 DNA-binding activity could be prolonged or diminished by chemical compounds either activating or inhibiting the activity of the longevity factor deacetylase SIRT1. These results suggest that SIRT1-mediated deacetylation of HSF1 could maintain HSF1 in a state competent for DNA-binding, thereby linking our research to HSF1-mediated regulation of lifespan. Currently, our focus is on a complex network of PTMs to decipher the post-translational signature of HSF1.

Unlike HSF1, which is a stable protein evenly expressed in most tissues and cell types, HSF2 shows a highly specific spatiotemporal expression pattern during development, and we have demonstrated that the amount of HSF2 is directly linked to its activity. Using mouse spermatogenesis as a model system, we have discovered an inverse correlation between the cell- and stage-specific wave- like expression patterns of HSF2 and a specific microRNA, miR-18, which is a member of the Oncomir-1/miR-17∼92 cluster. Intriguingly, miR-18 was found to repress the expression of HSF2 by directly targeting its 3’UTR. To investigate the in vivo function of miR-18, we developed a novel method T-GIST (Transfection of Germ cells in Intact Seminiferous Tubules) and were able to show that inhibition of miR-18 in intact mouse seminiferous tubules leads to increased HSF2 protein levels and altered expression of HSF2 target genes, including the Y-chromosomal multi-copy genes that we previously have reported as novel HSF2 targets in the testis. Our original finding that miR-18 regulates HSF2 activity in spermatogenesis links miR-18 to HSF2-mediated physiological processes and opens a whole new window of opportunities to elucidate the physiological and stress-related functions of HSF2, either alone or in conjunction with HSF1. Our studies on the formation of heterotrimers between HSF1 and HSF2 and their impact on already established and newly discovered targets genes should also shed light on the roles of HSFs in protein-misfolding disorders, such as neurodegenerative diseases, as well as in aging and cancer progression. So far, the studies have mostly concentrated on HSF1, but it is important to consider the existence of multiple HSFs and interactions between them, especially when searching for potential drugs to modify either expression or activity of these multi-faceted transcriptional regulators.

Funding:

The Academy of Finland, the Sigrid Jusélius Foundation, the Finnish Cancer Organizations, and Åbo Akademi University (Centre of Excellence in Cell Stress).

Collaborators:

Elisabeth Christians (University of Toulouse, France), Sampsa Hautaniemi (University of Helsinki), Susumu Imanishi and John

Eriksson (Åbo Akademi University), Noora Kotaja and Jorma Toppari (University of Turku), Pia Roos-Mattjus, Tiina Salminen, Peter Slotte and Kid Törnquist (Åbo Akademi University), Valérie Mezger (University of Paris Diderot, France), Jorma Palvimo (University of Eastern Finland), Sandy Westerheide and Rick Morimoto (Northwestern University, USA).

Selected Publications:

Björk J.K.*, Sandqvist A.*, Elsing A.N., Kotaja N. and Sistonen L. (2010) miR-18, a member of OncomiR-1, targets heat shock transcription factor 2 in spermatogenesis. Development, in press. Åkerfelt M., Morimoto R.I. and Sistonen L. (2010) Heat shock factors: integrators of cell stress, development and lifespan. Nat.

Rev. Mol. Cell Biol. 11: 545-555.

Blomster H.A.*, Imanishi S.Y.*, Siimes J., Kastu J., Morrice N.A., Eriksson J.E. and Sistonen L. (2010) In vivo identification of sumoylation sites by a signature tag and cysteine-targeted affinity purification. J. Biol. Chem. 285: 19324-19329.

Blomster H.A., Hietakangas V., Wu J., Kouvonen P., Hautaniemi S. and Sistonen L. (2009) Novel proteomics strategy brings insight into the prevalence of SUMO-2 target sites. Mol. Cell. Proteomics 8: 1382-1390.

Westerheide S.D.*, Anckar J.*, Stevens S.M.Jr., Sistonen L. and Morimoto R.I. (2009) Stress-inducible regulation of heat shock factor 1 by the deacetylase SIRT1. Science 323: 1063-1066. Sandqvist A., Björk J.K., Åkerfelt M., Chitikova Z., Grichine A., Vourc’h C., Jolly C., Salminen T.A., Nymalm Y. and Sistonen L. (2009) Heterotrimerization of heat-shock factors 1 and 2 provides a transcriptional switch in response to distinct stimuli. Mol. Biol. Cell 20: 1340-1347.

Åkerfelt M.*, Henriksson E.*, Laiho A., Vihervaara A., Rautoma K., Kotaja N. and Sistonen L. (2008) Promoter ChIP-chip analysis in mouse testis reveals Y chromosome occupancy by HSF2. Proc.

Natl. Acad. Sci. USA 105: 11224-11229.

Östling P.*, Björk J.K.*, Roos-Mattjus P., Mezger V. and Sistonen L. (2007) HSF2 contributes to inducible expression of hsp genes through interplay with HSF1. J. Biol. Chem. 282: 7077-7086. Chang Y.*, Östling P.*, Åkerfelt M., Trouillet D., Rallu M., Gitton Y., El Fatimy R., Fardeau V., Le Crom S., Morange M., Sistonen L. and Mezger V. (2006) Role of heat shock factor 2 in cerebral cortex formation and as a regulator of p35 expression. Genes Dev. 20: 836-847.

Anckar J.*, Hietakangas V.*, Denessiouk K., Thiele D.J., Johnson M.S. and Sistonen L. (2006) Inhibition of DNA binding by differential sumoylation of heat shock factors. Mol. Cell. Biol. 26: 955-964. Hietakangas V.*, Anckar J.*, Blomster H.A., Fujimoto M., Palvimo J.J., Nakai A. and Sistonen L. (2006) PDSM, a motif for phosphorylation-dependent SUMO modification. Proc. Natl. Acad.

Sci. USA 103: 45-50 (epub. Dec 21, 2005).

*equal contribution

From left to right, standing: Lea Sistonen, Eva Henriksson, Johanna Björk, Jenny Siimes, Malin Åkerfelt, Jenni Vasara, Alexsandra Elsing, Malin Blom, Aki Vartiainen, sitting: Johanna Ahlskog, Anton Sandqvist, Mikael Puustinen, Marek Budzynski.