"A nucleosome is the basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound in sequence around eight histone protein cores. This structure is often compared to thread wrapped around a spool."
http://en.wikipedia.org/wiki/Nucleosome

This model is based on Protein Data Bank entry 1KX5:
http://www.rcsb.org/pdb/explore.do?structureId=1kx5
There are separate STL files for the protein and DNA components.

Model created using VMD:
http://www.ks.uiuc.edu/Research/vmd/

Successfully made in PLA by a Replicator 2 using MakerWare 2.2.2.89. Standard resolution, 25% infill, 3 shells, raft and supports.

It may be tricky to fit the DNA model around the protein (Histone complex) model. If the DNA model snaps a little superglue can be used to fix it around the protein model.