Alexander "Sandy" D. Johnson is an American biochemist and Professor and Vice Chair of the Department of Microbiology and Immunology at the

University of California, San Francisco The University of California, San Francisco (UCSF) is a Public university, public Land-grant university, land-grant research university in San Francisco, California, United States. It is part of the University of California system and is dedic ...

. He is a member of the U.S.

National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...

Early life and education

Alexander D. Johnson was born in

Oak Ridge, Tennessee Oak Ridge is a city in Anderson County, Tennessee, Anderson and Roane County, Tennessee, Roane counties in the East Tennessee, eastern part of the U.S. state of Tennessee, about west of downtown Knoxville, Tennessee, Knoxville. Oak Ridge's po ...

in 1952. In 1970, Johnson enrolled as an undergraduate at

Vanderbilt University Vanderbilt University (informally Vandy or VU) is a private university, private research university in Nashville, Tennessee, United States. Founded in 1873, it was named in honor of shipping and railroad magnate Cornelius Vanderbilt, who provide ...

. He originally studied physics and mathematics; however, a summer as a technician in the laboratory of Howard E. Morgan convinced him to switch his area of study to molecular biology. He completed his

B.A. A Bachelor of Arts (abbreviated B.A., BA, A.B. or AB; from the Latin ', ', or ') is the holder of a bachelor's degree awarded for an undergraduate program in the liberal arts, or, in some cases, other disciplines. A Bachelor of Arts degree ...

in 1974. Johnson then moved on to a Ph.D. at

Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...

with

Mark Ptashne Mark Ptashne (born June 5, 1940, in Chicago) is a molecular biologist. He is the Ludwig Chair of Molecular Biology at Memorial Sloan–Kettering Cancer Center in New York City. Ptashne grew up in Chicago. He earned his undergraduate degree at R ...

working on the role of the Cro protein in regulating the phage

lytic cycle The lytic cycle ( ) is one of the two cycles of viral reproduction (referring to bacterial viruses or bacteriophages), the other being the lysogenic cycle. The lytic cycle results in the destruction of the infected cell and its membrane. Bacter ...

. In 1981, Johnson moved to the University of California, San Francisco to work as a

postdoctoral fellow A postdoctoral fellow, postdoctoral researcher, or simply postdoc, is a person professionally conducting research after the completion of their doctoral studies (typically a PhD). Postdocs most commonly, but not always, have a temporary academ ...

in the laboratory of Ira Herskowitz, working on gene regulation in the model yeast ''

Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungal microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have be ...

''. Johnson remained at the University of California, being appointed

assistant professor Assistant professor is an academic rank just below the rank of an associate professor used in universities or colleges, mainly in the United States, Canada, Japan, and South Korea. Overview This position is generally taken after earning a doct ...

in 1985,

associate professor Associate professor is an academic title with two principal meanings: in the North American system and that of the ''Commonwealth system''. In the ''North American system'', used in the United States and many other countries, it is a position ...

in 1991,

full professor Professor (commonly abbreviated as Prof.) is an academic rank at universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a 'person who professes'. Professors ...

in 1995, and Vice Chair of the Department of Microbiology and Immunology in 2003.

Research

Alexander Johnson is known for his work on gene regulation and cell biology in the yeast ''

Candida albicans ''Candida albicans'' is an opportunistic pathogenic yeast that is a common member of the human gut flora. It can also survive outside the human body. It is detected in the gastrointestinal tract and mouth in 40–60% of healthy adults. It is usu ...

''. Johnson's research group discovered a sexual mating cycle in ''C. albicans'' and characterized the genetic switch between the two ''C. albicans'' forms: white and opaque. His group has also investigated genes that allow ''C. albicans'' to survive and replicate inside mammalian hosts.

Notable publications

*Noble SM, French S... Johnson AD (2010). Systematic screens of a ''Candida albicans'' homozygous deletion library decouple morphogenetic switching and pathogenicity. ''Nature Genetics''. 42(7): pgs. 590-598 *Miller MG, Johnson AS (2002). White-opaque switching in ''Candida albicans'' is controlled by mating-type locus homeodomain proteins and allows efficient mating. ''Cell''. 110(3): pgs. 293-302 * Hull CM, Raisner RM, Johnson AD (2000). Evidence for mating of the 'asexual' yeast ''Candida albicans'' in a mammalian host. ''Science''. 289(5477): pgs. 307-310 *Braun BR, Johnson AD (1997). Control of filament formation in ''Candida albicans'' by the transcriptional repressor TUP1. ''Science''. 277(5322): pgs. 105-109 *Keleher CA, Redd MJ... Johnson AD (1992). Ssn6-Tup1 is a general repressor of transcription in yeast. ''Cell''. 68(4): pgs. 709-719

References

{{DEFAULTSORT:Johnson, Alexander D. Vanderbilt University alumni Harvard University alumni University of California, San Francisco faculty Living people Year of birth missing (living people) Fellows of the American Academy of Microbiology Members of the United States National Academy of Sciences