The GFP-NE81 fusion plasmid pIS191 containing the complete coding sequence of DDB_G0289429 (Schulz
et al., 2009b (
link)) was used as a starting point for all further constructs. For expression of NE81 in
E. coli, the complete coding sequence was cloned into pMALc2 (NEB, Frankfurt, Germany). Protein expression at room temperature and purification by amylose affinity chromatography was performed according to the manufacturer's instructions. The fusion protein was used for custom immunization of two rabbits (BioGenes, Berlin, Germany). Antisera were affinity-purified according to the manufacturer's instructions (GE Healthcare, München, Germany) using NHS-activated Sepharose with coupled MBP-NE81.
To generate the GFP-NE81ΔCLIM vector, pIS191 was used as a template for PCR amplification of the complete NE81 sequence, excluding the C-terminal CLIM motif, using
SalI-linker primer TAAATT
GTCGACTAATGGATATGTCAAAAAAGAAAAGTAAAC-3′ and
BamHI linker primer 5′-GCGC
GGATCCTTAATTTGATTTACCAGCTGAAGAAGG-3′. The PCR product was cloned into the N-terminal GFP-fusion vector pIS77 (Schulz
et al., 2009a (
link)) to yield pAK35 (G418 resistance).
The GFP-NE81ΔCLIM-S122A vector was generated after PCR amplification of two fragments of the NE81 sequence. The following primer combinations were used: fragment1 (385 base pairs):
SalI-linker primer (see above), 5′-GTTGAGCTGCTCTATTTGGTG
CTAATGGTG-3′; fragment2 (1808 base pairs): 5′-CACAAATAGGTACACCATTA
GCACCAAATAG-3′;
BamHI-linker primer; the exchanged bases yielding the S122A point mutation are underlined. The amplified fragments were used as templates for an overlap extension PCR using the
SalI- and
BamHI-linker primers. The PCR product was cloned into the N-terminal GFP-fusion vector pIS77 (Schulz
et al., 2009a (
link)) to yield pPB14-29.
To generate the GFP-NLS-CP224ΔC, two complementary oligonucleotides were annealed (5′-TAAATTGTCGACAAC GTAAGAGAAAGAGATCAAAAGAGCTCAATTTA-3′, 5′-TAAATTGAGCTCTTTTGATCTCTTTCTCTTA CGTTGTCGACAATTTA-3′) and cloned with
SalI and
SacI into the GFP-CP224ΔC vector (Hestermann and Gräf, 2004 (
link)) to yield pPB45-7.
The homologous recombination vector, containing a blasticidin S resistance cassette flanked by genomic fragments of the NE81 gene, was constructed in pLPBLP (Faix
et al., 2004 (
link)). Suitable linker primers were used to amplify genomic
Dictyostelium DNA fragments by PCR. The 5′
SaII/
HindIII fragment consisted of 820 base pairs of 5′ noncoding sequence starting at base position −852, and the 3′
PstI/
BamHI fragment comprised 679 base pairs of coding sequence ending at base position 2353 of the genomic sequence. The resulting knockout plasmid (pAK43) was digested with
PvuII prior to transformation into
Dictyostelium cells.
For expression in human cells, the AT-rich NE81 sequence was codon-optimized for expression in mammalian cells by gene synthesis (DNA2.0, Menlo Park, CA) and cloned into pEGFP-C2 (BD Biosciences, Heidelberg, Germany).
Krüger A., Batsios P., Baumann O., Luckert E., Schwarz H., Stick R., Meyer I, & Gräf R. (2012). Characterization of NE81, the first lamin-like nucleoskeleton protein in a unicellular organism. Molecular Biology of the Cell, 23(2), 360-370.