Abstract
The nuclear basket (NB) scaffold, a fibrillar structure anchored to the nuclear pore complex (NPC), is regarded as constructed of polypeptides of the coiled-coil dominated protein TPR to which other proteins can bind without contributing to the NB’s structural integrity. Here we report vertebrate protein ZC3HC1 as a novel inherent constituent of the NB, common at the nuclear envelopes (NE) of proliferating and non-dividing, terminally differentiated cells of different morphogenetic origin. Formerly described as a protein of other functions, we instead present the NB component ZC3HC1 as a protein required for enabling distinct amounts of TPR to occur NB-appended, with such ZC3HC1-dependency applying to about half the total amount of TPR at the NEs of different somatic cell types. Furthermore, pointing to an NB structure more complex than previously anticipated, we discuss how ZC3HC1 and the ZC3HC1-dependent TPR polypeptides could enlarge the NB’s functional repertoire.
Highlights
Reciprocal Dependence with TPR.The nuclear pore complex (NPC) is a macromolecular structure that serves as the gateway for exchanging material between the nucleus and cytoplasm in eukaryotes
Such nuclear envelopes (NE) can be further treated with RNases and non-ionic detergents, which in buffers maintaining nuclear basket (NB) integrity allows for much of the membrane lipids to be extracted while still leaving the NPCs and their NBs intact (Figure 1(A2))
While technical features related to sample processing and sectioning for post-embedding immuno-transmission electron microscopy (iTEM), in addition to potential biological causes, might have contributed to such spread distribution, we considered the possibility that such mean value might reflect the mean of two adjoining Gaussian peaks, with their flanks overlapping in such a manner that the individual peaks could not be clearly resolved by iTEM
Summary
Reciprocal Dependence with TPR.The NPC is a macromolecular structure that serves as the gateway for exchanging material between the nucleus and cytoplasm in eukaryotes. Its core structure forming the actual translocation channel through the NE is flanked by ring-like structures on its nuclear and cytoplasmic side. Both rings serve as anchor sites for fibrillar appendices arranged in eight-fold rotational symmetry but distinct from each other in appearance and composition. Observed and described as nuclear fibrils or as either fish trap- or basket-like structures associated with the NPCs in vertebrate tumour cells and oocytes (e.g., [1,2,3,4,5,6,7]), findings of NBs in insect salivary gland cells (e.g., [8]), in Saccharomyces cerevisiae [9], and in the protozoan Dictyostelium [10] indicate that the NB is common to many eukaryotes and probably present in a wide range of cell types
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