Formation and distribution of nuclear pore complexes in interphase

Area of Science:

• Cell Biology
• Molecular Biology
• Cytology

Background:

• Nuclear pores regulate molecular transport between the nucleus and cytoplasm.
• Previous assumptions suggested nuclear pore complex distribution in somatic cells is random.
• The timing and distribution patterns of nuclear pore formation require further investigation.

Purpose of the Study:

• To investigate nuclear pore formation during interphase in lymphocytes.
• To evaluate the distribution pattern of nuclear pore complexes in somatic animal cells.
• To identify potential sites of nuclear pore formation in interphase nuclei.

Main Methods:

• Freeze-etching technique applied to control and phytohemagglutinin (PHA)-stimulated lymphocytes.
• Computer analysis of freeze-etched rat kidney cells to assess nuclear pore distribution.
• Analysis of sectioned human melanoma cells using criteria for prospective pore sites.

Main Results:

• Lymphocytes stimulated with PHA showed a twofold increase in nuclear pores per nucleus during interphase.
• Nuclear pore distribution in rat kidney cells exhibited nonrandom spacing, with frequent center-to-center distances of approximately 1300 Å.
• Evidence of forming nuclear pores was observed in human melanoma cells, correlating with membrane specialization and heterochromatin alterations.

Conclusions:

• Nuclear pore formation is demonstrated to occur during interphase in lymphocytes.
• Nuclear pore complex distribution in somatic cells is nonrandom, potentially reflecting underlying chromosomal organization.
• A mechanism for nuclear pore formation during interphase, independent of nuclear membrane reformation, exists.