MCB 9506236 Karl Johnson Molecular chaperones of the 70,000 M.W. Heat Shock Protein (HSP70) family are special proteins that interact with many other types of proteins in cells to assist both their proper folding and assembly. Biological processes known to require HSP70 function include such diverse examples as response to stress, protein targeting and secretion, assembly of steroid hormone receptors, viral replication and the initiation of gene transcription. Recent evidence implicates members of the HSP70 chaperone family in the construction of larger intracellular structures such as the microtubule cytoskeleton. During an investigation into the assembly of a microtubule-containing organelle, the eukaryotic flagellum of the green alga Chlamydomonas, an HSP70 family member was identified. Immunofluorescent localization experiments demonstrated that this HSP70 protein was concentrated in the tips of flagella. This localization is significant, as previous work has shown that the tips are the sites of flagellar assembly. A combination of molecular, cytological and cell biological techniques will be employed to further characterize the in vivo role of this molecular chaperone. This investigation offers significant opportunities for novel insight into the processes which govern cytoskeletal assembly in living cells. Because flagella are present on many different cell types, including cells of the human body, investigations in the green alga Chlamydomonas should reveal details about conserved processes of macromolecular assembly applicable to understanding the formation of other microtubule-containing structures, such as the mitotic spindle or interphase microtubule cytoskeleton. %%% Living cells are dynamic systems that contain architectural elements that give them form and shape. These structures must be assembled and disassembled at appropriate times and places in order for the cells to function properly. This investigation examines the role a special kind of protein called a "chape rone" may play in this process. This project should further our understanding of normal cellular functions and address a key mechanism in life. ***
