= Naoko Tanaka
{c}
Naoko Tanaka is a <biochemist> credited with identifying <RtcB> as an <RNA ligase> in joint work with <Stewart Shuman>. The original 2011 publication names both authors and their Sloan-Kettering molecular-biology affiliation. It tested a concrete biochemical function for a previously uncharacterized <protein> associated with an <RNA repair> gene cluster.<RtcB is the RNA ligase component of an Escherichia coli RNA repair operon by Naoko Tanaka and Stewart Shuman>[Published byline, affiliations and Abstract]{ref}
The experimental question was whether <RtcB> itself could join broken <RNA>. The researchers tested a broken <tRNA>-like <stem-loop> with cyclic-phosphate and hydroxyl ends, then separated labelled substrate and ligated product by <denaturing polyacrylamide gel electrophoresis>. Product analysis supported formation of a normal 3′,5′ <phosphodiester bond> at the joined site. This demonstrated a chemical activity; the initial paper treated broader physiological repair roles as proposals rather than as facts established for every organism.<RtcB is the RNA ligase component of an Escherichia coli RNA repair operon by Naoko Tanaka and Stewart Shuman>[Abstract; Figures 1 and 3, labelled product analysis and junction chemistry]{ref}
The labelling design gives an illuminating counting example. The reported broken substrate contained a labelled $19$-<nucleotide> strand and an unlabelled $20$-<nucleotide> partner. Joining them produces a $39$-<nucleotide> strand but does not double the number of labels per molecule.<RtcB is the RNA ligase component of an Escherichia coli RNA repair operon by Naoko Tanaka and Stewart Shuman>[Figure 1C, two strands of the broken substrate]{ref} If an invented measurement gives $30$ corrected label units in product and $70$ in unjoined labelled substrate, the inferred joined fraction is $30/(30+70)=0.30$, assuming equal recovery and label detection. Multiplying the product signal by $39/19$ would instead introduce an inappropriate length correction: the label counts molecules carrying that label, not their total <RNA> mass.
Tanaka's credited experiment exemplifies a productive move from a genomic association to a testable <enzyme> function. The observed chemical product supplies evidence that a neighboring-gene argument alone cannot provide.
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