our laboratory studies the biosynthesis and cellular roles of trna n6-threonylcarbamoyladenosine (t6a), which is a necessary post-transcriptional modification universally found in ann-decoding trnas in the three domains of life. the t6a is located 3'-adjacent to the anticodon triplet in the anticodon stem loop of trnas, wherein it plays pivotal roles in preventing the u33 and a37 from unwanted watson-crick pairing as well as in enhancing the base pairing between anticodon triplet from trna and codon triplet from mrna. the absence or interfered making of trna t6a gravely affects cellular proteostasis and causes cell death, is also implicated in the growth and development of higher eukaryotes, and a set of human diseases, i.e. galloway-mowat syndrome.
the two last universal common ancestor (luca) families tsac/sua5 and tsad/kae1/qri7 form a minimal duet to catalyze the substrates of l-threonine, bicarbonate, atp and trna to make trna t6a, during which a short-lived intermediate l-threonylcarbamoyladenylate (tc-amp) is necessarily generated to couple the chemical transformations. however, the molecular mechanisms and machinery workings underlying trna t6a biosynthesis might vary among different life systems, as additional organism-specific enzymes are needed for the enzymatic reconstitution of trna t6a. the enzymes function in ensemble, namely protein complex, either stable or dynamic. intriguingly, the kae1-mediated pentameric or octameric keops complex and tsad-mediated ternary tsad-b-e complex may also possess other important molecular functions apart from the crystal-clear one in catalyzing the trna t6a biosynthesis, such as keops' role promoting telomere elongation in yeast.
we have aggregated ample knowledge and sophisticated techniques in dissecting the structure–activity relationship of trna t6a-modifying enzymes over the past decade. our lab people are doggedly focused on analyzing the structure-function relationship of these ancient luca enzymes, and on elucidating the sequential assembly and regulatory layers of the trna t6a biosynthetic machinery as well. furthermore, we are exploring the possible novel functions of keops complex and the cellular implications of trna t6a and other important t6a derivative modifications (i.e. ht6a, m6t6a, ms2t6a, ct6a, ms2ct6a) pathway by applying an array of approaches and techniques in molecular biology, enzymology, structural biology, cellular biology and genetics.