Mechanical forces are known to play a significant role in biological processes. These forces can be transmitted to the cell through the cytoskeletal filament network, inducing different biochemical responses within the cytoplasm. Although there have been ample reports showing that cytoplasmic enzymes can be directly activated by a local stress on the cell surface via integrins, there has been no evidence that mechanical forces can directly alter nuclear functions without intermediate biochemical cascades. Recently, we showed evidence that forces on the cell membrane can be transmitted directly into the nucleus, inducing structural changes of protein complexes in Cajal bodies. Here, we describe a protocol that utilizes the optical magnetic twisting cytometry (MTC) for force application and fluorescent resonance energy transfer (FRET) to monitor the dynamics and interaction of various Cajal body proteins.