Greider then completed her postdoctoral work, and also held a faculty position, at the Cold Spring Harbor Laboratory, Long Island, New York. Greider continued to study "Tetrahymena" telomerase, cloning the gene encoding the RNA component and demonstrating that it provided the template for the TTGGGG telomere repeats (1989) as well as establishing that telomerase is processive (1991). She was also able to reconstitute "Tetrahymena" telomerase "in vitro" (1994) and define the mechanisms of template utilization (1995). Greider also worked with Calvin Harley to show that telomere shortening underlies cellular senescence (1990). To further test this idea mouse and human telomerase were characterized (1993) (1995) and the mouse telomerase RNA component was cloned (1995).