THE DEVELOPMENTALLY-REGULATED DROSOPHILA EMBRYONIC NUCLEAR LAMINA PROTEIN YOUNG ARREST (FS(1)YA) IS CAPABLE OF ASSOCIATING WITH CHROMATIN

The Drosophila fs(1)Ya protein (YA) is an essential component of the e arly embryonic nuclear lamina. Mutant zygotes lacking functional YA ar rest in the first division cycles following fertilization, hence havin g a '(Y) under bar oung (A) under bar rrest' of their development. The nuclear lamina is thought to act as the structural backbone for the n ucleus and to provide anchoring sites for interphase chromosomes. Here , we demonstrate in vitro that YA is not required for the de novo form ation of nuclear structures. Since YA's sequence predicts potential DN A binding motifs, this protein may instead function to connect the lam ina and chromosomes, and thus aid in organizing the nucleus. We ectopi cally expressed YA in polytene cells and demonstrated its association with polytene chromosomes, preferentially at interbands. Furthermore, our in vitro studies indicate that embryonic YA protein is capable of associating with decondensed chromatin. These observations suggest tha t YA may be required for the interaction between chromatin and the nuc lear envelope during early embryogenesis.