Replication and transcription depend on attachment of DNA to the nuclear cage.

When living cells are lysed in a non-ionic detergent and 2 M-NaCl, structures are released that resemble nuclei. They contain naked nuclear DNA packaged within a flexible cage of RNA and protein. Since the DNA is supercoiled, it must be intact and looped by attachment to the cage. It is argued that this cage is the active site of the key nuclear functions, transcription and replication: outlying sequences are activated by attachment to polymerases at the cage. This thesis is supported by the close and specific association of nascent RNA with cages, the attachment of active viral sequences (in transformed and productively infected cells) and the attachment of nascent DNA during both normal and repair synthesis.