In 1961, Richardson obtained aPublic Health Service fellowship underArthur Kornberg in his biochemistry laboratory atStanford Medical School. As a result, Richardson and Ingrid Hanssum moved toPalo Alto. In Kornberg's lab, Richardson focused on improving the purification technique ofDNA polymerase fromE. coli. In Kornberg's lab, Richardson worked alongsidePaul Berg,Reiji andTsunko Okazaki, and several others. In 1964, Richardson left Kornberg's lab and began a faculty position atHarvard Medical School, where he was promoted to tenure in 1967. Richardson served as chairman of the department ofbiological chemistry from 1978 to 1987. Additionally, Richardson served as editor or associate editor of theAnnual 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 bacteriophageT7 RNA polymerase in 1985. Richardson used the T7 RNA polymerase/promoter system to control the expression of aphage 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 withrifampicin'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 inE. coli cells expressing T7 RNA polymerase. Richardson proposed the T7 RNA polymerase/promoter system as an "attractive alternative" to the mini- ormaxicell.[16]
A couple years later, Richardson researched a self-made DNA polymerase for potential use in DNA sequencing. This highlyprocessive DNA polymerase was composed of an 84-kDa T7 gene 5 protein and 12-kDaE. 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 thechain-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 ofDNA probes, and lack of background pause sites and uniform distribution of dideoxy-terminated fragments.[18]
In 1998, Richardson examined thecrystal 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 anucleoside triphosphate in the polymeraseactive 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 forphosphoryl transfer by related polymerases with metal.[19]
More recently in 2011, Richardson developed a single-molecule assay to measure the activity of thereplisome withfluorescently-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]
