PMID: 3321068Dec 1, 1987Paper

Constitutive expression of the yeast HEM1 gene is actually a composite of activation and repression

Proceedings of the National Academy of Sciences of the United States of America
T Keng, L Guarente

Abstract

We show that HEM1 (encoding 5-aminolevulinate synthase) expression, while constitutive under all steady-state growth conditions tested, is activated by the HAP2-HAP3 global activation system that controls expression of apocytochromes. This finding creates a paradox because apocytochrome activation by HAP2-HAP3 is highly regulated, subject to induction by heme, and subject to further derepression by a shift from glucose medium to one containing a nonfermentable carbon source. We clarify this issue by showing that HEM1 is subject to two additional layers of control that mask regulatory changes. First is a second activation system acting at a site close to the HAP2-HAP3 target sequence that keeps HEM1 turned on under conditions of heme deficiency. Second is a regulated negative control site downstream of the upstream activation site that counteracts derepression in medium containing a nonfermentable carbon source. Thus, transcription of the constitutive gene is actually a composite of opposing regulatory sites. This complex regulatory arrangement may exist to allow HEM1 to be coordinated transiently with apocytochromes for transition to respiratory growth. Conversely, it may reflect the alteration of HEM1 from a regulated to a con...Continue Reading

References

Dec 1, 1985·Proceedings of the National Academy of Sciences of the United States of America·S HahnL Guarente
Dec 11, 1974·Biochemical and Biophysical Research Communications·H R Mahler, C C Lin
Dec 1, 1984·Proceedings of the National Academy of Sciences of the United States of America·L Guarente, E Hoar
Jul 1, 1983·Proceedings of the National Academy of Sciences of the United States of America·J L Teem, M Rosbash

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Citations

Feb 1, 1990·Current Genetics·J R MattoonD Guthrie
Jan 1, 1996·Folia Microbiologica·P Haviernik, G J Laquin
Mar 1, 1991·Proceedings of the National Academy of Sciences of the United States of America·D M BeckerL Guarente
Apr 4, 1998·Nucleic Acids Research·R Mantovani
Jan 2, 2003·The Plant Cell·Raymond W KwongJohn J Harada
Jul 1, 1989·European Journal of Biochemistry·L A Grivell
Aug 15, 1992·European Journal of Biochemistry·H J BussinkJ Visser
Aug 29, 2012·Oxidative Medicine and Cellular Longevity·M Isabel González Siso, M Esperanza Cerdán
Jun 21, 2011·Applied Microbiology and Biotechnology·Angelique C W FrankenSandra de Weert
Apr 21, 2006·The Plant Journal : for Cell and Molecular Biology·Orna Ben-NaimEliezer Lifschitz
Aug 1, 1997·Yeast·M González-DomínguezM E Cerdán
Aug 1, 1992·Molecular & General Genetics : MGG·T KengR Larocque
Mar 1, 1997·Methods : a Companion to Methods in Enzymology·R S ZitomerP M Snow
May 1, 1989·Molecular and Cellular Biology·M R HodgeM G Cumsky
Jun 1, 1989·Molecular and Cellular Biology·B Repetto, A Tzagoloff
Apr 1, 1995·Journal of Bacteriology·B A Schilke, T J Donohue
Oct 1, 1990·Molecular and Cellular Biology·M R HodgeM G Cumsky
Aug 1, 1990·Molecular and Cellular Biology·B Repetto, A Tzagoloff
Mar 1, 1992·Microbiological Reviews·R S Zitomer, C V Lowry

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