In 1961, Richardson obtained a Public Health Service fellowship under Arthur Kornberg in his biochemistry laboratory at Stanford Medical School. As a result, Richardson and Ingrid Hanssum moved to Palo Alto. In Kornberg's lab, Richardson focused on improving the purification technique of DNA polymerase from E. coli. In Kornberg's lab, Richardson worked alongside Paul Berg, Reiji and Tsunko Okazaki, and several others. In 1964, Richardson left Kornberg's lab and began a faculty position at Harvard Medical School, where he was promoted to tenure in 1967. Richardson served as chairman of the department of biological chemistry from 1978 to 1987. Additionally, Richardson served as editor or associate editor of the Annual Review of Biochemistry from 1972 to 2003. As of 2020, Richardson continues his position as professor at Harvard Medical School.[1] Richardson taught four doctoral students: Dennis M. Livingston, David N. Frick, Richard D. Colodner, and Paul L. Modrich.[3]
Richardson's most highly-cited accomplishment was made while working with bacteriophage T7 RNA polymerase in 1985. Richardson used the T7 RNA polymerase/promoter system to control the expression of a phage T7 gene 5 protein (gp5), which is a subunit of T7 DNA polymerase. By combining the specificity of T7 RNA polymerase for its own promoters with rifampicin's ability to selectively inhibit the host RNA polymerase, Richardson established a method to exclusively express genes, specifically the phage T7 gene 5 protein, under the control of the T7 RNA polymerase promoter. During this process, Richardson constructed a T7 phage with deletions in gene 1 that propagate in E. coli cells expressing T7 RNA polymerase. Richardson proposed the T7 RNA polymerase/promoter system as an "attractive alternative" to the mini- or maxicell.[16]
A couple years later, Richardson researched a self-made DNA polymerase for potential use in DNA sequencing. This highly processive DNA polymerase was composed of an 84-kDa T7 gene 5 protein and 12-kDa E. colithioredoxin at a one-to-one stoichiometric ratio.[17] In his study, Richardson demonstrated that this modified DNA polymerase would be ideal for DNA sequencing by the chain-termination method. Richardson based this finding off of three main factors: high processivity and lack of associated exonuclease activity, ability to use low concentrations of radioactive nucleotides for preparation of DNA probes, and lack of background pause sites and uniform distribution of dideoxy-terminated fragments.[18]
In 1998, Richardson examined the crystal structure of a bacteriophage T7 DNA replication complex at 2.2 Å resolution. Before imaging, Richardson complexed the T7 bacteriophage DNA polymerase with a primer-template and a nucleoside triphosphate in the polymerase active site. Through analysis of the crystal structure, Richardson determined how the replication complex selects nucleotides in a template-directed manner. Furthermore, Richardson established an understanding of the basis for phosphoryl transfer by related polymerases with metal.[19]
More recently in 2011, Richardson developed a single-molecule assay to measure the activity of the replisome with fluorescently-labeled DNA polymerases. Richardson then used this assay to quantify the process of polymerase exchange. Richardson determined that soluble polymerases are recruited to an actively synthesizing replisome, which leads to a polymerase exchange event between the excess polymerases and the synthesizing polymerase after about 50 seconds. This supports the belief that replisomes are highly dynamic complexes.[20]