INTERACTIONS AMONG DROSOPHILA NUCLEAR-ENVELOPE PROTEINS LAMIN, OTEFIN, AND YA

The nuclear envelope plays many roles, including organizing nuclear st ructure and regulating nuclear events. Molecular associations of nucle ar envelope proteins may contribute to the implementation of these fun ctions. Lamin, otefin, and YA are the three Drosophila nuclear envelop e proteins known in early embryos. We used the yeast two-hybrid system to explore the interactions between pairs of these proteins. The ubiq uitous major lamina protein, lamin Dm, interacts with both otefin, a p eripheral protein of the inner nuclear membrane, and YA, an essential, developmentally regulated protein of the nuclear lamina. In agreement with this interaction, lamin and otefin can be coimmunoprecipitated f rom the vesicle fraction of Drosophila embryos and colocalize in nucle ar envelopes of Drosophila larval salivary gland nuclei. The two-hybri d system was further used to map the domains of interaction among lami n, otefin, and YA. Lamin's rod domain interacts with the complete otef in protein, with otefin's hydrophilic NH2-terminal domain, and with tw o different fragments derived from this domain. Analogous probing of t he interaction between lamin and YA showed that the lamin rod and tail plus part of its head domain are needed for interaction with full-len gth YA in the two-hybrid system. YA's COOH-terminal region is necessar y and sufficient for interaction with lamin. Our results suggest that interactions with Iamin might mediate or stabilize the localization of otefin and YA in the nuclear lamina. They also suggest that the need for both otefin and lamin in mediating association of vesicles with ch romatin might reflect the function of a protein complex that includes these two proteins.