Abstract
ABSTRACT Lamins interact with the nuclear membrane and chromatin but the precise players and mechanisms of these interactions are unknown. Here, we tested whether the removal of the CaaX motif from Lamin B disrupts its attachment to the nuclear membrane and affects chromatin distribution. We used Drosophila melanogaster LamA25 homozygous mutants that lack the CaaX box. We found that the mutant Lamin B was not confined to the nuclear periphery but was distributed throughout the nuclear interior, colocalizing with chromosomes in salivary gland and proventriculus. The peripheral position of Lamin C, nuclear pore complex (NPC), heterochromatin protein 1a (HP1a), H3K9me2- and H3K27me3-associated chromatin remained intact. The fluorescence intensity of the DAPI-stained peripheral chromatin significantly decreased and that of the central chromatin significantly increased in the proventriculus nuclei of the mutantflies compared to wild-type. However, the mutation had little effect on chromatin radial distribution inside highly polytenized salivary gland nuclei.
Highlights
The nuclear lamina is an important structural component of the nuclear envelope in the metazoan cell nucleus
The type A lamin is encoded by the gene Lamin C, and the type B lamin is encoded by the gene Lamin [2,10]
We suggest that the mutant Lamin B, which is associated with polytene chromosomes, may attract a portion of nuclear pore complex (NPC) toward the nuclear interior in salivary glands
Summary
The nuclear lamina is an important structural component of the nuclear envelope in the metazoan cell nucleus It consists of a large num ber of proteins, including lamins – the major building blocks of the nuclear lamina – and asso ciated transmembrane and chromatin-binding proteins [1,2,3]. There are two known types of lamin proteins: A- and B-type Both lamin types contain an ⍺-helical rod domain between the N-terminal head domain and the C-terminal tail domain. All currently known invertebrate species have one B-type lamin gene [2], except for Tunicates, which have two B-type lamin genes (L1 and L2), where L1 encodes for two protein var iants, L1α and L1β [9].
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