Alterations in nuclear matrix structure after adenovirus infection

Abstract

Infection of HeLa cells with adenovirus serotype 2 causes rearrangements in nuclear matrix morphology which can best be seen by gentle cell extraction and embedment-free section electron microscopy. We used these techniques to examine the nuclear matrices and cytoskeletons of cells at 6, 13, 28, and 44 h after infection. As infection progressed, chromatin condensed onto the nucleoli and the nuclear lamina. Virus-related inclusions appeared in the nucleus, where they partitioned with the nuclear matrix. These virus centers consisted of at least three distinguishable areas: amorphously dense regions, granular regions whose granulations appeared to be viral capsids, and filaments connecting these regions to each other and to the nuclear lamina. The filaments became decorated with viral capsids of two different densities, which may be empty capsid shells and capsids with DNA-protein cores. The interaction of some capsids with the ifiaments persisted even after lysis of the cell. We propose that granulated virus-related structures are sites of capsid assembly and storage and that the filaments may be involved in the transport of capsids and capsid intermediates. The nuclear lamina became increasingly crenated after infection, with some extensions appearing to bud off and form blebs of nuclear material in the cytoplasm. The perinuclear cytoskeleton became rearranged after infection, forming a corona of decreased filament number around the nucleus. In summary, we propose that adenovirus rearranges the nuclear matrix and cytoskeleton to support its own replication.

Core filaments of the nuclear matrix.

“…We have also seen nuclear filaments in adenovirus-infected HeLa cells (Zhai et al, 1987) as chromatin retracts, leaving filaments uncovered. At later stages of adenovirus infection these filaments are decorated with adenovirus nucleocapsids.…”

Adenovirus and minute virus of mice DNAs are localized at the nuclear periphery

“…Additionally, recent EM studies on the nuclear matrix architecture of Ad2-infected HeLa cells (21) indicated that Ad2 capsids throughout the nucleus were associated with each other and the nuclear envelope by filaments. From all these data we suggest that Ad2 DNA replication sites are associated with the nuclear envelope but that the replicated DNA can be extended into the nuclear interior as it is 'reeled through' fixed replication sites (reviewed in 1).…”

The nuclear matrix of Euglena gracilis (Euglenophyta): A stage of nuclear matrix evolution?

“…Output of the equipment and sonic treatment time of the cells were determined by EM detecting of the effect of the second extraction (usually 'Output control' 2.5 for 2 min was suitable for 10 mL cells in CSK at 2.0 x 10 6 cells/mL). The sequential extractions were performed as described by Zhai et al (1987) with some modifications. Briefly the steps are as follows: 1) sonicated cells were collected by centrifugation (600 g, 5 min) and suspended in CSK-Triton buffer (CSK buffer containing 0.5% (vol/vol) Triton X-100) and extracted for 5 min at 0°C.…”