0.03 to 0.1 μm^2/sec
||Gorski SA, Dundr M, Misteli T. The road much traveled: trafficking in the cell nucleus. Curr Opin Cell Biol. 2006 Jun18(3):284-90 p.286 right column 2nd paragraphPubMed ID16621498
|| Molenaar C, et al., Poly(A)+ RNAs roam the cell nucleus and pass through speckle domains in transcriptionally active and inactive cells. J Cell Biol. 2004 Apr 26 165(2):191-202.  Shav-Tal Y, et al. Dynamics of single mRNPs in nuclei of living cells. Science. 2004 Jun 18 304(5678):1797-800.  Vargas DY, et al. Mechanism of mRNA transport in the nucleus. Proc Natl Acad Sci U S A. 2005 Nov 22 102(47):17008-13.PubMed ID15117966, 15205532, 16284251
||"...several independent labeling and imaging methods..."
||"Most RNA molecules are rapidly exported from the nucleus after their synthesis. The fact that newly synthesized, fully processed messenger RNAs can be detected in the cytoplasm within a few minutes after their generation inspired the notion that mRNA, rRNA and tRNA movement within the nucleus might be directed in order to increase transport efficiency. Directed, energy-dependent transport of RNAs within the cell nucleus has now largely been debunked. In pioneering studies, Politz and Pederson labeled endogenous polyadenylated RNAs by in vivo hybridization using a poly(T)-oligonucleotide and demonstrated energy-independent diffusional motion [refs 39,40]. These results have been confirmed by several independent labeling and imaging methods and a diffusion coefficient of ~0.03–0.1µm^2/s has been determined [primary sources], suggesting that energy-independent movement, probably diffusion, is sufficient to effectively transport a mRNA from its sites of transcription to the nuclear pore [ref 44] (Figure 1b)."