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Papers by Stefanie Hauser

Journal of Animal Science, 1999

Gonzalo Castillo, Stefanie Hauser, Jennifer K Rosenfield and Bruce M Spiegelman Role and Regulati... more Gonzalo Castillo, Stefanie Hauser, Jennifer K Rosenfield and Bruce M Spiegelman Role and Regulation of PPARy During Adipogenesis ... Role and Regulation of PPARy During Adipogenesis Gonzalo Castillo, Stefanie Hauser, Jennifer K. Rosenfield, and Bruce M. Spiegelman&amp;amp;#x27; ...

J Biol Chem, 2005

E2F6, a member of the E2F-family of transcription factors, is a retinoblastoma protein-independen... more E2F6, a member of the E2F-family of transcription factors, is a retinoblastoma protein-independent transcriptional repressor. E2F6 associates with polycomb group (Pc-G) multiprotein complexes that contain histone H3 methyltransferases, suggesting that E2F6 represses genes by covalent histone modification. However, genes that are repressed by E2F6 via a mechanism that involves histone H3 methylation have not been identified. Using cDNA microarray experiments comparing wild-type and E2f6؊/؊ mouse embryonic fibroblasts, we now found that E2F6 is required to silence the meiosis-specific genes SMC1␤ and STAG3 in somatic cells. Re-expression of E2F6 in E2f6؊/؊ cells was sufficient to restore their repression. E2F6 binds in vivo to the promoters of these genes through a conserved binding site. Transcriptional repression of SMC1␤ and STAG3 by E2F6 involves multiple mechanisms, including methylation of histone H3 on lysine 9 and lysine 27. Our findings suggest a molecular mechanism for the stable transcriptional silencing of meiotic genes in somatic cells by E2F6.

The EMBO journal, Jan 15, 1995

Translocation of proteins across the endoplasmic reticulum membrane is initiated by the signal re... more Translocation of proteins across the endoplasmic reticulum membrane is initiated by the signal recognition particle (SRP), a cytoplasmic ribonucleoprotein complex consisting of a 7S RNA and six polypeptides. To investigate the functions of the SRP components, we have tested the activities of several SRP subparticles. We show that the SRP GTPase (SRP54) alone binds a signal sequence and discriminates it from a non-signal sequence. Although SRP54 alone is unable to promote translocation, SRP54 in a complex with SRP RNA is both necessary and sufficient to promote translocation of an elongation-arrested nascent protein in a GTP-regulated manner. For co-translational translocation, additional SRP components are required. We discuss the implications of our results for the function of the Escherichia coli SRP which is homologous to the SRP54/SRP-RNA complex.

Molecular and cellular biology, 2010

The retinoblastoma tumor suppressor protein (pRB) and related p107 and p130 "pocket proteins... more The retinoblastoma tumor suppressor protein (pRB) and related p107 and p130 "pocket proteins" function together with the E2F transcription factors to repress gene expression during the cell cycle and development. Recent biochemical studies have identified the multisubunit DREAM pocket protein complexes in Drosophila melanogaster and Caenorhabditis elegans in regulating developmental gene repression. Although a conserved DREAM complex has also been identified in mammalian cells, its physiological function in vivo has not been determined. Here we addressed this question by targeting Lin9, a conserved core subunit of DREAM. We found that LIN9 is essential for early embryonic development and for viability of adult mice. Loss of Lin9 abolishes proliferation and leads to multiple defects in mitosis and cytokinesis because of its requirement for the expression of a large set of mitotic genes, such as Plk1, Aurora A, and Kif20a. While Lin9 heterozygous mice are healthy and normal,...

The EMBO Journal, 2004

Genetic studies in Caenorhabditis elegans identified lin-9 to function together with the retinobl... more Genetic studies in Caenorhabditis elegans identified lin-9 to function together with the retinoblastoma homologue lin-35 in vulva differentiation. We have now identified a human homologue of Lin-9 (hLin-9) and provide evidence about its function in the mammalian pRB pathway. hLin-9 binds to pRB and cooperates with pRB in flat cell formation in Saos-2 cells. In addition, hLin-9 synergized with pRB and Cbfal to transactivate an osteoblast-specific reporter gene. In contrast, hLin-9 was not involved in pRBmediated inhibition of cell cycle progression or repression of E2F-dependent transactivation. Consistent with these data, hLin-9 was able to associate with partially penetrant pRB mutants that do not bind to E2F, but retain the ability to activate transcription and to promote differentiation. hLin-9 can also inhibit oncogenic transformation, dependent on the presence of a functional pRB protein. RNAimediated knockdown of Lin-9 can substitute for the loss of pRB in transformation of human primary fibroblasts. These data suggest that hLin-9 has tumor-suppressing activities and that the ability of hLin-9 to inhibit transformation is mediated through its association with pRB.

The EMBO Journal, 2007

Regulated gene expression is critical for the proper timing of cell cycle transitions. Here we re... more Regulated gene expression is critical for the proper timing of cell cycle transitions. Here we report that human LIN-9 has an important function in transcriptional regulation of G2/M genes. Depletion of LIN-9 by RNAi in human fibroblasts strongly impairs proliferation and delays progression from G2 to M. We identify a cluster of G2/M genes as direct targets of LIN-9. Activation of these genes is linked to an association between LIN-9 and B-MYB. Chromatin immunoprecipitation assays revealed binding of both LIN-9 and B-MYB to the promoters of G2/M regulated genes. Depletion of B-MYB recapitulated the biological outcome of LIN-9 knockdown, including impaired proliferation and reduced expression of G2/M genes. These data suggest a critical role for human LIN-9, together with B-MYB, in the activation of genes that are essential for progression into mitosis.

Proceedings of the National Academy of Sciences, 1996

Correct folding of newly synthesized proteins is proposed to be assisted by molecular chaperones ... more Correct folding of newly synthesized proteins is proposed to be assisted by molecular chaperones and folding catalysts. To identify cellular factors involved in the initial stages of this process we searched for proteins associated with nascent polypeptide chains. In an Escherichia coli transcription/translation system synthesizing p-galactosidase we identified a 58-kDa protein which associated with translating ribosomes but dissociated from these ribosomes upon release of nascent 3-galactosidase. N-terminal sequencing identified it as trigger factor, previously implicated in protein secretion. Direct evidence for association of trigger factor with nascent polypeptide chains was obtained by crosslinking. In a wheat germ translation system complemented with E. coli lysates, e-4-(3-trifluoromethyldiazirino)benzoic acid-lysine residues were incorporated into nascent secretory preprolactin and a nonsecretory preprolactin mutant. Trigger factor crosslinked to both types of nascent chains, provided they were ribosome bound. Trigger factor contains key residues of the substrate-binding pocket of FK506-binding protein-type peptidyl-prolyl-cis/trans-isomerases and has prolyl isomerase activity in vitro. We propose that trigger factor is a folding catalyst acting cotranslationally.

Oncogene, 2012

The DREAM complex is an important regulator of mitotic gene expression during the cell cycle. Her... more The DREAM complex is an important regulator of mitotic gene expression during the cell cycle. Here we report that inactivation of LIN9, a subunit of DREAM, results in premature senescence, which can be overcome by the SV40 large T (LT) antigen. Together with the observation that p16 INK4a and p21 Waf1 are upregulated upon loss of LIN9, these results indicate that senescence is triggered by the pRB and p53 tumor suppressor pathways. We also find that LIN9-null cells that escape senescence are chromosomally instable because of compromised mitotic fidelity. SV40 LT-expressing cells that adapt to the loss of LIN9 can grow anchorage-independently in soft agar, a hallmark of oncogenic transformation. Taken together, these results suggest an important role of mitotic gene regulation in the maintenance of genomic stability and tumor suppression.

Journal of Cellular Biochemistry, 1994

Vascular endothelial growth factor (VEGF) is a newly identified growth and permeability factor wi... more Vascular endothelial growth factor (VEGF) is a newly identified growth and permeability factor with a unique specificity for endothelial cells. Recently the flt-encoded tyrosine kinase was characterized as a receptor for VEGF. A novel tyrosine kinase receptor encoded by the KDR gene was also found to bind VEGF with high affinity when expressed in CMT-3 cells. Screening for flt and KDR expression in a variety of species and tissue-derived endothelial cells demonstrates that flt is predominantly expressed in human placenta and human vascular endothelial cells. Placenta growth factor (PIGF), a growth factor significantly related to VEGF, is coexpressed with flt in placenta and human vascular endothelial cells. KDR is more widely distributed and expressed in all vessel-derived endothelial cells. These data demonstrate that cultured human endothelial cells isolated from different tissues express both VEGF receptors in relative high levels and, additionally, that all investigated nonhuman endothelial cells in culture are also positive for KDR gene expression.

Growth Factors, 1993

Placenta Growth Factor (PlGF) was recently discovered as a secreted growth factor for vascular en... more Placenta Growth Factor (PlGF) was recently discovered as a secreted growth factor for vascular endothelial cells and based on its homology to vascular endothelial growth factor (VEGF), can be classified as a new member of this growth factor family. We have carried out polymerase chain amplification (PCR) of RNA from human umbilical vein endothelial cells and placenta tissue and discovered a second species of PlGF, PlGF-2. PlGF-2 has a 21-amino acid insertion not present in PlGF-1 coding for a highly basic region near the C-terminus. This is similar to VEGF189. Northern analysis has shown, that the PlGF gene is expressed only in a limited number of cell types and tissues, e.g. human umbilical vein endothelial cells (HUVE) and placenta. Infection of Sf158 insect cells with recombinant baculoviruses specific for the two forms showed, that both, PlGF-1 and PlGF-2 are secreted efficiently into the supernatant and PlGF-2 can bind with high affinity to heparin. Both PlGF forms had a similar mitogenic potency for bovine aortic endothelial cells. Binding studies with 125I-VEGF165 demonstrate, that supernatant of PlGF expressing insect cells can compete for receptor binding. Similar to VEGF, PlGF can exist in different forms which are probably generated by differential splicing. The occurrence of two molecular forms of this endothelial specific growth factor suggests different physiological roles of the two forms during placental development and differentiation.

Journal of cell science, Jan 15, 2012

The mammalian DREAM complex is key regulator of cell cycle regulated gene transcription and drive... more The mammalian DREAM complex is key regulator of cell cycle regulated gene transcription and drives the expression of many gene products required for mitosis and cytokinesis. In this study we characterized a novel target gene of DREAM, GAS2L3, which belongs to the GAS2 family of proteins with putative actin and microtubule binding domains. We found that GAS2L3 localizes to the spindle midzone and the midbody during anaphase and cytokinesis, respectively. Biochemical studies show that GAS2L3 binds to and bundles microtubules as well as F-actin in vitro. Strikingly, the RNAi-mediated knock-down of GAS2L3 results in chromosome segregation defects, in multinucleated cells and cells with multi-lobed nuclei. Likewise, chronic downregulation of GAS2L3 causes chromosome loss and aneuploidy. Time-lapse video microscopy experiments in GAS2L3 knock-down cells reveal abnormal oscillation of chromatin and the spindle during cytokinesis. Taken together, our data reveal novel, important roles of GA...