Head


Cornelis Calkhoven
Cornelis Calkhoven

Postdocs

Christine Müller

PhD Students

Anna Bremer

Götz Hartleben

Kyungmin In

Sandra Schreiber

Laura Zidek

Diploma Students

Doreen Jahn

Technicians

Sabrina Eichwald



 

Calkhoven Laboratory

Eukaryotic gene regulation

 

Translational control of gene expression

The aetiologies of several human diseases, including cancer, have been linked with mutations in genes of the translational control machinery or in cis-regulatory sequences of mRNAs. Our aim is to determine the signalling pathways that control the expression of C/EBPα and -β transcription factors and the NAD+-dependent protein deacetylase Sirt1, which are key-regulators in the triad of metabolism, cancer and ageing. In our research we combine molecular and cell biological techniques with physiological studies in cell culture and mouse models.

 

 

Projects

Genetically engineered mice deficient in the C/EBPα and -β uORF
Within the family of C/EBP transcription factors only c/ebpα and -β genes are intronless and have a cis-regulatory uORF in their mRNA’s 5’-leader sequence for translational controlled expression: Three protein isoforms, extended, full-length and truncated, of the C/EBPα and -β transcription factors are expressed from alternative translation initiation sites. The full-length C/EBPs activate (metabolic) genes and induce proliferation arrest, they are considered to be tumour suppressors. The truncated C/EBPs, on the other hand, repress genes and promote proliferation, and can act as oncogenes. Knock-In mice deficient of the uORF of the c/ebpβ gene have been generated and the equivalent Knock-In mice for c/ebpα are currently constructed. We examine how abrogation of uORF-mediated C/EBP-translation affects glucose and energy homeostasis as well as cancer susceptibility in vivo.

Translational control of C/EBP through metabolic signalling pathways
Nutrient and energy signalling through mTOR (mammalian target of rapamycin) converge on the translational control machinery to adapt global and specific mRNA-translation to the energy- and nutritional state of the cell. Cancer cells have overcome the usual restriction by nutrients and energy checkpoints, allowing them to proliferate and maintain high metabolic rates even when nutrients and energy are short. We study how hormone and growth factor signals as well as nutrient availability regulate C/EBP isoform expression and how this affects cell physiology through regulation of the downstream target genes.
maus1

Sub-cellular localisation and function of C/EBP proteins
The physiological function of the extended C/EBPα isoform and the regulation of its expression from an alternative CUG-codon are poorly studied. We identified a conserved nucleolar-retention signal that is required and sufficient for nucleolar retention of exclusively the extended isoform. Our current research aims to determine the function of Extended-C/EBPα in ribosome biogenesis and the identification of functional partners. In addition, we address the unsolved questions about the regulation of CUG-codon use for translation initiation.
maus2

Regulation of translation through the 3’UTR
We investigate the role of the 3’UTR (3’-untranslated region) in regulated translation of the C/EBPs as well as Sirt1, particularly in response to nutrient availability and caloric restriction. Sirt1 and C/EBPs are both critically involved in the regulation of metabolic and stress genes. In lower eukaryotes Sirt1 orthologues are important regulators of lifespan determination, and it mediates several of the known beneficial effects of caloric restriction in diverse organisms up to mammals.
maus3

 

Recent selected publications

  • Müller C, Bremer A, Schreiber S, Eichwald S and Calkhoven CF (2010) Nucleolar retention of a translational C/EBPα isoform stimulates rDNA transcription and cell size. EMBO J. pub ahead of print [PubMed]
  • Wethmar K, Bégay V, Smink JJ, Zaragoza K, Wiesenthal V, Dörken B, Calkhoven CF and Leutz A (2010) C/EBPβΔuORF mice - a genetic model for uORF-mediated translational control in mammals. Genes Dev. 24, 15-20.[PubMed]
  • van Gorp AGM, van der Vos KE, Brenkman AB, Bremer A, van den Broek N, Zwartkruis F, Hershey JW, Burgering BMT, Calkhoven CF and Coffer PJ (2009) AGC kinases regulate phosphorylation and activation of eukaryotic translation initiation factor 4B. Oncogene 28, 95-106.[PubMed]
  • Wiesenthal V, Leutz A, Calkhoven CF (2006) A translation control reporter system (TCRS) for the analysis of translationally controlled processes in the vertebrate cell. Nucleic Acids Res. 34, e23. [PubMed]
  • Wiesenthal V, Leutz A, Calkhoven CF (2006) Analysis of translation initiation using a translation control reporter system (TCRS). Nat Protoc. 1, 1531-1537. [PubMed]
  • Jundt F, Raetzel N, Müller C, Calkhoven CF, Kley K, Mathas S, Lietz A, Leutz A, Dörken B (2005) A rapamycin derivative (everolimus) controls proliferation through down-regulation of truncated CCAAT enhancer binding protein β and NF-κB activity in Hodgkin and anaplastic large cell lymphomas. Blood. 106, 1801-1807. [PubMed]
  • Müller C, Calkhoven CF, Sha X, Leutz A (2004) The CCAAT enhancer-binding protein α (C/EBPα) requires a SWI/SNF complex for proliferation arrest. J Biol Chem. 279, 7353-7358. [PubMed]
  • Calkhoven CF§, Müller C§, Martin R, Krosl G, Pietsch H, Hoang T, Leutz A (2003) Translational control of SCL isoform expression in hematopoietic lineage choice. Genes Dev. 17, 959-964. [PubMed] §shared first author
  • Calkhoven CF*, Müller C, Leutz A (2002) Translational control of gene expression and disease. Trends Mol Med. 8, 577-583. [PubMed] *corresponding author
  • Calkhoven CF, Müller C, Leutz A* (2000) Translational control of C/EBPα and C/EBPβ isoform expression. Genes Dev. 14, 1920-1932. [PubMed] *corresponding author

 

Last update: March 19, 2008
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