Johnson was a principal investigator in the laboratory of molecular biology at the National Cancer Institute from 1996 to 2007.

Alfred Charles Johnson, the 12th in a family of 14 children, grew up near Selma, Alabama, where he attended a segregated high school.

[2] His dissertation was titled Hormonal responsiveness of developmentally regulated genes in fetal rat liver.

[3] Johnson conducted his doctoral research at the biology division of Oak Ridge National Laboratory.

He joined the National Institutes of Health (NIH) in 1985 as an American Cancer Society postdoctoral fellow.