Involved in cytoskeletal rearrangements required for lymphocyte migration in response of chemokines. Activates RAC1 and RAC2, but not CDC42, by functioning as a guanine nucleotide exchange factor (GEF), which exchanges bound GDP for free GTP. May also participate in IL2 transcriptional activation via the activation of RAC2. Homodimer (Probable). Interacts with RAC1 and RAC2. Interacts with CRKL and VAV. Interacts with CD3Z (By similarity). Colocalizes with F-actin. Specifically expressed in hematopoietic cells. The DOCKER domain probably mediates the GEF activity. Belongs to the DOCK family.