Presented scientific silhouettes awarded the 2001 Nobel Prize in physiology and medicine ? Leland Hartwell , Paul Nurse'a and Timothy Hunt , the pioneers of molecular mechanisms regulating the cell cycle . Their research mainly due to the detection of protein serine- threonine kinases called cyklinozależnymi , due to the regulation of their activity by specific protein ? cyclins . These kinases subsequently proved to be essential for normal cell cycle progression . Classic has become the concepts introduced by Hartwell START cycle checkpoints .