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Results for “Nuclear Localization Signals”

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PubMedDate not supplied

Cell uptake and radiotoxicity studies of an nuclear localization signal peptide-intercalator conjugate labeled with [99mTc(CO)3]+.

A trifunctional bioconjugate consisting of the SV40 nuclear localization signal (NLS) peptide, an aliphatic triamine ligand, and the DNA intercalating pyrene has been synthesized and quantitatively labeled with [(99m)Tc(OH(2))(3)(CO)(3)](+). The radiotoxicity of the resulting nucleus-targeting radiopharmaceutical on B16F1 mouse melanoma cells has been investigated to evaluate the activity of Auger and Coster-Kronig electrons on the viability of cells. We found a dose-dependent significant radiotoxicity of the nucleus-targeting radiopharmaceutical clearly related to the low energy decay of (99m)Tc. These principal results imply a possible therapeutic strategy based on the use of the low-energy Auger electron-emitting (99m)Tc radionuclide attached to nucleus-targeting molecules and comprising an intercalator. Highly efficient DNA targeting vectors could complement the usual role of (99m)Tc in diagnostic applications. The Auger electrons emitted by the (99m)Tc nuclide induce DNA damage leading ultimately, through a mitotic catastrophe pathway, to necrotic cell death. Non-DNA-targeting (99m)Tc complexes display much lower radiotoxicity.

Animals↗

PubMed2005

Identification of novel nuclear localization signal within the ErbB-2 protein.

ErbB2, a member of the receptor tyrosine kinase family, is frequently over-expressed in breast cancer. Proteolysis of the extracellular domain of ErbB2 results in constitutive activation of ErbB2 kinase. Recent study reported that ErbB2 is found in the nucleus. Here, we showed that ErbB2 is imported into the nucleus through a nuclear localization signal (NLS)-mediated mechanism. The NLS sequence KRRQQKIRKYTMRR (aa655-668) contains three clusters of basic amino acids and it is sufficient to target GFP into the nucleus. However, mutation in any basic amino acid cluster of this NLS sequence significantly affects its nuclear localization. Furthermore, it was found that this NLS is essential for the nuclear localization of ErbB2 since the intracellular domain of Erb2 lacking NLS completely abrogates its nuclear translocation. Taken together, our study identified a novel nuclear localization signal and reveals a novel mechanism underlying ErbB2 nuclear trafficking and localization.

Amino Acids↗

PubMed2001

[Amino acid sequence analysis of peptides that can react to the nuclear localization signals of human cytomegalovirus PPUL44].

OBJECTIVE: To find the peptides that have strong binding ability to the nuclear localization signals (NLS) of human Cytomegalovirus (HCMV) PPUL44 protein, and to analyze their amino acid sequences. METHODS: Peptide clones that have binding ability to the NLSs were selected from a random peptide display library by using synthesized HCMV PPUL44 NLSA and NLSB respectively. The DNA sequences of these clones were detected by using "ABI Prism BigDye Terminator Cycle Sequencing Ready Reaction Kit". The amino acid sequences of the clones were analyzed for their homology, and the homologous sequences were compared with known sequences in protein bank. RESULTS: The peptides that can bind to the HCMV PPUL44 NLSA(named as bNLSApep) have higher homologous amino acid sequence to importin alpha subunit, the bNLSApep48 sequence AVVTPVLTEILK is more similar to the sequence of the importin alpha subunit Arm 7 from amino acid 18 to 29, ANIFPVLTEILQ; The bNLSBpep 39 is similar to the sequence of all 8 Arm regions of importin alpha subunit from amino acid 10 to 21. CONCLUSION: It is possible that the HCMV PPUL44 NLSA is a specific recognition site by importin alpha subunit, it can bind to the Arm 7 region of importin alpha subunit; HCMV PPUL44 NLSB is a non-specific recognition site for importin alpha subunit. This study provided an experimental data for the proposal that the Arm repeat region of importin alpha subunit is the binding region of NLS.

Amino Acid Sequence↗

PubMed2006

Structural and functional analyses of Kaposi sarcoma-associated herpesvirus ORF57 nuclear localization signals in living cells.

Kaposi sarcoma-associated herpesvirus (KSHV) ORF57 is a multifunctional, nuclear protein involved in post-transcriptional regulation of a subset of viral genes during lytic replication. Three nuclear localization signals (NLSs), NLS1 (amino acids (aa 101-107), NLS2 (aa 121-130), and NLS3 (aa 143-152), were identified in the N terminus of the ORF57 protein, and each of the three represents a short stretch of basic amino acid residues. Disruption of all three NLSs prevented localization of ORF57 in the nucleus. Insertion of individual NLSs into a heterologous cytoplasmic protein converted it into a nuclear protein, confirming that each NLS functions independently and is sufficient to promote protein nuclear localization. Although it exhibits a function similar to that of Epstein-Barr virus EB2 in promoting KSHV ORF59 expression, KSHV ORF57 differs from the herpes simplex virus ICP27 protein, and its function could be disrupted by point mutations of single or two NLSs in random combination, despite the proper localization of the mutant protein in the nucleus. The dysfunctional ORF57 containing NLS mutations also had low affinity with ORF59 RNA and the RNA export factor REF. However, the REF binding of ORF57 in vivo appeared to have no effect on ORF57-mediated enhancement of ORF59 expression. Thus, the three NLSs identified in ORF57 provide at least two functions, nuclear localization of ORF57 and up-regulation of ORF59 expression.

Active Transport, Cell Nucleus↗

PubMed1996

Functional analysis of eukaryotic 20S proteasome nuclear localization signal.

The 20S proteasome is widely viewed at as a cytoplasmic multicatalytic proteinase complex: immunocytochemical investigations, however, show that proteasomes are localized in the cytoplasm as well as in the nucleus within the same cell. Strong nuclear accumulation of proteasomes is observed in rapidly dividing cells such as in the early stages of Drosophila embryogenesis and in tumorigenic cells. In fact, dependent on the metabolic state of a certain tissue or cell type its cellular distribution appears differentially regulated. Several of the proteasomal alpha-type subunits carry putative nuclear localization signals which may or may not take part in the regulation of the intracellular distribution of 20S proteasomes. We have examined the functional role of the putative nuclear localization signal (NLS) -KKKQKK-in the Drosophila PROS-28.1 subunit by deletion mutagenesis and transfection experiments. Linkage of the putative PROS-28.1 NLS to BSA as reporter protein and in vitro import studies with permeabilized mouse NIH 3T3 cells show that this NLS is able to induce complete translocation of the reporter protein into the cell nucleus. For analysis of the NLS within the 28-kDa subunit, cDNA deletion constructs were cloned into a pSG5 expression vector and transiently transfected into mouse fibroblast cells. Whereas the deletion of the NLS alone resulted only in a slight impairment of subunit transport into the nucleus, removal of the C-terminal 96 amino acid residues abolished nuclear translocation completely.

3T3 Cells↗

PubMed2006

Nuclear import of Epstein-Barr virus nuclear antigen 1 mediated by NPI-1 (Importin alpha5) is up- and down-regulated by phosphorylation of the nuclear localization signal for which Lys379 and Arg380 are essential.

Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA-1) is essential for replication of episomal EBV DNAs and maintenance of latency. Multifunctional EBNA-1 is phosphorylated, but the significance of EBNA-1 phosphorylation is not known. Here, we examined the effects on nuclear translocation of Ser phosphorylation of the EBNA-1 nuclear localization signal (NLS) sequence, 379Lys-Arg-Pro-Arg-Ser-Pro-Ser-Ser386. We found that Lys379Ala and Arg380Ala substitutions greatly reduced nuclear transport and steady-state levels of green fluorescent protein (GFP)-EBNA1, whereas Pro381Ala, Arg382Ala, Pro384Ala, and Glu378Ala substitutions did not. Microinjection of modified EBNA-1 NLS peptide-inserted proteins and NLS peptides cross-linked to bovine serum albumin (BSA) showed that Ala substitution for three NLS Ser residues reduced the efficiency of nuclear import. Similar microinjection analyses demonstrated that phosphorylation of Ser385 accelerated the rate of nuclear import, but phosphorylation of Ser383 and Ser386 reduced it. However, transfection analyses of GFP-EBNA1 mutants with the Ser-to-Ala substitution causing reduced nuclear import efficiency did not result in a decrease in the nuclear accumulation level of EBNA-1. The results suggest dynamic nuclear transport control of phosphorylated EBNA-1 proteins, although the nuclear localization level of EBNA-1 that binds to cellular chromosomes and chromatin seems unchanged. The karyopherin alpha NPI-1 (importin alpha5), a nuclear import adaptor, bound more strongly to Ser385-phosphorylated NLS than to any other phosphorylated or nonphosphorylated forms. Rch1 (importin alpha1) bound only weakly and Qip1 (importin alpha3) did not bind to the Ser385-phosphorylated NLS. These findings suggest that the amino-terminal 379Lys-Arg380 is essential for the EBNA-1 NLS and that Ser385 phosphorylation up-regulates nuclear transport efficiency of EBNA-1 by increasing its binding affinity to NPI-1, while phosphorylation of Ser386 and Ser383 down-regulates it.

Amino Acid Substitution↗

PubMed1996

Comparative mutagenesis of nuclear localization signals reveals the importance of neutral and acidic amino acids.

Nuclear proteins contain information within their primary structures which causes them to accumulate selectively in the nucleus [1,2] by associating with the cytosolic receptor importin [3]. The alpha subunit of importin binds the nuclear localization signal (NLS), and the beta subunit docks at the nuclear pore complex. The NLS of the simian virus 40 large T-antigen (SV40 T-ag) is a single cluster of basic amino acids (PKKKRKV132; single-letter code, the basic amino acids are shown in bold; [4,5]), whereas the NLS of nucleoplasmin is bipartite. The nucleoplasmin NLS requires two essential clusters of basic amino acids, separated by a mutation-tolerant spacer (KRPAATKKAGQAKKKK171; [6] [7]). A SwissProt database search shows that more than 50% of nuclear proteins contain a match to this consensus, and many NLSs have since been found to conform to this type of motif in yeast, plants and animals [8-10]. A different NLS (PAAKRVKLD) has been reported in the oncoprotein c-Myc, but it has received little attention because, unlike other known NLSs, only three of nine residues are basic [11], and one residue is even acidic. Here, we report that constructs containing an inactive basic cluster downstream of the bipartite signal of nucleoplasmin can be directed to the nucleus by flanking them with specific neutral and acidic residues taken from the signal reported for c-Myc. Nuclear targeting by the single cluster KKKK is dependent on it being preceded by PAA and is stimulated if it is followed by the dipeptide LD. The relative positions of these elements are crucial to the function of these NLSs. All regions of the unconventional signal of c-Myc are functionally important. Contrary to conventional views, neutral and even acidic amino acids can play crucial roles in NLSs.

Amino Acid Sequence↗

PubMed1992

I kappa B/MAD-3 masks the nuclear localization signal of NF-kappa B p65 and requires the transactivation domain to inhibit NF-kappa B p65 DNA binding.

The active nuclear form of the NF-kappa B transcription factor complex is composed of two DNA binding subunits, NF-kappa B p65 and NF-kappa B p50, both of which share extensive N-terminal sequence homology with the v-rel oncogene product. The NF-kappa B p65 subunit provides the transactivation activity in this complex and serves as an intracellular receptor for a cytoplasmic inhibitor of NF-kappa B, termed I kappa B. In contrast, NF-kappa B p50 alone fails to stimulate kappa B-directed transcription, and based on prior in vitro studies, is not directly regulated by I kappa B. To investigate the molecular basis for the critical regulatory interaction between NF-kappa B and I kappa B/MAD-3, a series of human NF-kappa B p65 mutants was identified that functionally segregated DNA binding, I kappa B-mediated inhibition, and I kappa B-induced nuclear exclusion of this transcription factor. Results from in vivo expression studies performed with these NF-kappa B p65 mutants revealed the following: 1) I kappa B/MAD-3 completely inhibits NF-kappa B p65-dependent transcriptional activation mediated through the human immunodeficiency virus type 1 kappa B enhancer in human T lymphocytes, 2) the binding of I kappa B/MAD-3 to NF-kappa B p65 is sufficient to retarget NF-kappa B p65 from the nucleus to the cytoplasm, 3) selective deletion of the functional nuclear localization signal present in the Rel homology domain of NF-kappa B p65 disrupts its ability to engage I kappa B/MAD-3, and 4) the unique C-terminus of NF-kappa B p65 attenuates its own nuclear localization and contains sequences that are required for I kappa B-mediated inhibition of NF-kappa B p65 DNA binding activity. Together, these findings suggest that the nuclear localization signal and transactivation domain of NF-kappa B p65 constitute a bipartite system that is critically involved in the inhibitory function of I kappa B/MAD-3. Unexpectedly, our in vivo studies also demonstrate that I kappa B/MAD-3 binds directly to NF-kappa B p50. This interaction is functional as it leads to retargeting of NF-kappa B p50 from the nucleus to the cytoplasm. However, no loss of DNA binding activity is observed, presumably reflecting the unique C-terminal domain that is distinct from that present in NF-kappa B p65.

Animals↗

PubMed2006

Classical nuclear localization signals: definition, function, and interaction with importin alpha.

The best understood system for the transport of macromolecules between the cytoplasm and the nucleus is the classical nuclear import pathway. In this pathway, a protein containing a classical basic nuclear localization signal (NLS) is imported by a heterodimeric import receptor consisting of the beta-karyopherin importin beta, which mediates interactions with the nuclear pore complex, and the adaptor protein importin alpha, which directly binds the classical NLS. Here we review recent studies that have advanced our understanding of this pathway and also take a bioinformatics approach to analyze the likely prevalence of this system in vivo. Finally, we describe how a predicted NLS within a protein of interest can be confirmed experimentally to be functionally important.

Active Transport, Cell Nucleus↗

PubMed2006

Identification of a nuclear localization signal in mouse polycomb protein, M33.

The mouse Polycomb group (PcG) protein M33 forms nuclear complexes with the products of other PcG members and maintains repressed states of developmentally important genes, including homeotic genes. In this context, nuclear localization is a prerequisite for M33 to exert its function. However, we previously found that M33 in mouse liver shuttles dynamically between the nucleus and the cytoplasm, depending on the proliferative states of cells, coupled with phosphorylation and dephosphorylation of M33 protein. To understand the mechanism and significance of this phenomenon, we identified the functional nuclear localization signal (NLS) of M33 protein. Deletion mutants that lack a particular one of three putative NLS motifs failed to localize in the nucleus. Green fluorescent protein (GFP) fused to this motif specifically localized in the nucleus. We conclude that this amino-acid stretch in M33 acts as the functional NLS for this protein.

Animals↗

PubMed2005

Requirement of an additional Sam68 domain for inhibition of human immunodeficiency virus type 1 replication by Sam68 dominant negative mutants lacking the nuclear localization signal.

Human immunodeficiency virus type 1 (HIV-1) replication requires active nuclear export of unspliced and incompletely spliced HIV-1 RNA transcripts. This process is evolutionally made possible by expression of HIV-1 Rev, one of the three HIV-1 proteins encoded by completely spliced HIV-1 RNAs. Evidence has accumulated to suggest that Sam68 plays an important role in HIV-1 replication through HIV-1 Rev protein. In the present study, we further examined the structure-function relationship of Sam68 protein in relation to HIV-1 replication. We identified a Sam68 domain located between aa269 and aa321 to be involved in the HIV-inhibitory effects of Sam68 dominant negative mutants lacking the nuclear localization signal (NLS). Deletion of this domain abrogated inhibition of HIV-1 replication by these mutants. HIV-1 Rev protein appeared to mediate the HIV-inhibitory effects of these mutants and by this domain, as assessed by Rev-dependent chloramphenicol acetyltransferase reporter gene assay, in trans rev-defective HIV-1 complementation assay, and RNase protection assay. The HIV-inhibitory mutants containing this domain were further found to have diminished binding affinity to the wild-type Sam68 and to be associated with cytoplasmic retention of exclusively nuclear localized wild type Sam68. Taken together, these results further ascertain the important role of Sam68 in HIV-1 Rev function and viral replication, and suggest that the HIV-inhibitory effects of Sam68 dominant negative mutants directly result from their binding to endogenous Sam68 and their interference with nuclear localization of endogenous Sam68.

Adaptor Proteins, Signal Transducing↗

PubMedDate not supplied

[Large subunit of translation initiation factor--3 p170 contains potentially functional nuclear localization signals].

Eukaryotic translation factors and their subunits can have independent cellular functions, including regulation of nuclear events. We analyzed primary structure of p170 large subunit of human translation initiation factor eIF3 and found four potential bipartite nuclear localization signals (NLS). Then we studied whether these NLS were functional, that is were able to direct protein to cell nucleus. Complementary DNA of p170 fragments were expressed in cultured CV-1 and Cos-1 green monkey cells, and localization of fused with GFP proteins was determined by fluorescent microscopy. We established that p170 molecule possessed at least two functional NLS which determined nuclear localization of p170 fragments. At the same time more long p170 fragments containing the same functional NLS could be retained in cytoplasm. We speculate that either using specific factors or after limited proteolysis p170 can enter cell nucleus and participate in genome expression regulation. Also we do not exclude the possibility that functioning of p170 in cytoplasm can be regulated by reversible binding of importins to its NLS.

Animals↗

PubMed1995

The identification of a functional nuclear localization signal in the Huntington disease protein.

Positional cloning has shown that the Huntington disease (HD) mutation is an expanded trinucleotide repeat in the IT15 gene. Although this mutation clearly produces the HD phenotype, the function of the Huntington disease protein remains undefined. One recent immunocytochemical study suggested that the IT15 protein preferentially localizes to the nucleus of affected neuronal cells. If this result is accurate, it could link the biochemical function of this protein to nuclear activities such as gene regulation. To examine the nuclear transport of the Huntington disease protein, we searched for basic peptide motifs that could produce nuclear localization. One peptide (RRKGKEK) was identified that is highly homologous to a consensus nuclear localization signal. When fused to the cytoplasmic reporter protein, beta-galactosidase, nuclear localization was observed in stably transformed human cell lines. In a complementary study, an anti-peptide polyclonal antibody, raised against a sequence adjacent to the putative nuclear localization sequence, detected the IT15 protein in the nucleus of human cells. These results extend and confirm the previous localization studies and identify an IT15 peptide motif that can function for nuclear localization.

Amino Acid Sequence↗

PubMed2000

A novel nuclear localization signal in human DNA topoisomerase I.

DNA topoisomerase (topo) I is a nuclear enzyme that plays an important role in DNA metabolism. Based on conserved nuclear targeting sequences, four classic nuclear localization signals (NLSs) have been proposed at the N terminus of human topo I, but studies with yeast have suggested that only one of them (amino acids (aa) 150-156) is sufficient to direct the enzyme to the nucleus. In this study, we expressed human topo I fused to enhanced green fluorescent protein (EGFP) in mammalian cells and demonstrated that whereas aa 150-156 are sufficient for nuclear localization, the nucleolar localization requires aa 157-199. More importantly, we identified a novel NLS within aa 117-146. In contrast to the classic NLSs that are rich in basic amino acids, the novel NLS identified in this study is rich in acidic amino acids. Furthermore, this novel NLS alone is sufficient to direct not only EGFP into the nucleus but also topo I; and the EGFP.topo I fusion driven by the novel NLS is as active in vivo as the wild-type topo I in response to the topo I inhibitor topotecan. Together, our results suggest that human topo I carries two independent NLSs that have opposite amino acid compositions.

Amino Acid Sequence↗

PubMed1993

Endogenous axoplasmic proteins and proteins containing nuclear localization signal sequences use the retrograde axonal transport/nuclear import pathway in Aplysia neurons.

When the nuclear localization signal peptide (sp) of the SV 40 large T antigen was coupled to human serum albumin (HSA), rhodaminated (r), and microinjected into axons of Aplysia neurons in vitro, the rHSA-sp was conveyed through the axon to the cell body and then into the nucleus (Ambron et al., 1992). But since rHSA-sp is an artificial construct, we needed to determine whether naturally occurring nuclear proteins use this pathway. We therefore injected calf thymus histone H-1 and Xenopus oocyte nucleoplasmin into axons. By 3 hr both were retrogradely transported and targeted into the nucleus, though histone H-1 less efficiently than rHSA-sp or nucleoplasmin. In contrast, neither rHSA, nor rHSA conjugated to a peptide with a random distribution of basic amino acids, was transported or imported. To see if proteins that use the pathway remain intact, we coupled sp to HRP. When injected into varicosities, the HRP-sp was transported/imported to the nucleus, where it was enzymatically active. A key issue was to determine whether endogenous proteins use this pathway. Consequently, axoplasm was extruded from Aplysia nerves and the proteins were fractionated by size. SDS-PAGE and Western blots showed that two fractions contained proteins that were recognized by an affinity-purified antibody to sp: fraction 3 included sp83, and fraction 4 contained sp75. In addition, these two proteins were found in nuclei isolated from neurons. To assess transport, the total proteins in the fractions were rhodaminated and injected into varicosities. Fraction 3, but not fraction 4, contained protein that was transported through the axon to the nucleus.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1995

Two nuclear localization signals present in the basic-helix 1 domains of MyoD promote its active nuclear translocation and can function independently.

MyoD, a member of the family of helix-loop-helix myogenic factors that plays a crucial role in skeletal muscle differentiation, is a nuclear phosphoprotein. Using microinjection of purified MyoD protein into rat fibroblasts, we show that the nuclear import of MyoD is a rapid and active process, being ATP and temperature dependent. Two nuclear localization signals (NLSs), one present in the basic region and the other in the helix 1 domain of MyoD protein, are demonstrated to be functional in promoting the active nuclear transport of MyoD. Synthetic peptides spanning these two NLSs and biochemically coupled to IgGs can promote the nuclear import of microinjected IgG conjugates in muscle and nonmuscle cells. Deletion analysis reveals that each sequence can function independently within the MyoD protein since concomittant deletion of both sequences is required to alter the nuclear import of this myogenic factor. In addition, the complete cytoplasmic retention of a beta-galactosidase-MyoD fusion mutant protein, double deleted at these two NLSs, argues against the existence of another functional NLS motif in MyoD.

Amino Acid Sequence↗

PubMed1997

C/EBP proteins contain nuclear localization signals imbedded in their basic regions.

The C/EBP-related proteins (C/EBPalpha, CRP1, C/EBPbeta, and C/EBPdelta) form a subfamily of bZIP (basic region/leucine zipper) transcription factors that display sequence homology within the bZIP domain. The conserved basic region contains two motifs that exhibit significant homology to the bipartite nuclear localization signal (NLS) first described in nucleoplasmin. CRP1 and C/EBPbeta proteins bearing deletions of the basic region accumulate in the cytoplasm, in contrast to their normal nuclear location. Analysis of chimeric proteins consisting of CRP1 basic region sequences fused to beta-galactosidase revealed that the CRP1 basic region contains a single NLS that differs from conventional bipartite signals in two ways. First, mutation of a pair of arginine residues at the N-terminus of the proposed NLS does not disrupt its function. Second, the CRP1 NLS requires additional nonbasic residues at its C-terminus. A basic residue within the CRP1 NLS that is not conserved within the C/EBP family is occupied instead by an uncharged residue in C/EBPalpha and C/EBPbeta. When this nonconserved arginine residue was changed to alanine the CRP1 NLS behaved as a classical bipartite signal, suggesting that bipartite NLSs are present in all family members but that NLSs of the individual members differ slightly. Additionally, mutation of critical NLS residues in the intact CRP1 and C/EBPbeta proteins showed that these elements exhibit more bipartite-like characteristics when present in their normal sequence context. Finally, we observed that a C/EBPbeta protein lacking its NLS can be localized to the nucleus when coexpressed with C/EBPalpha, indicating that a single NLS is sufficient to promote nuclear transport of a bZIP dimer.

Amino Acid Sequence↗

PubMed2006

Identification of a nuclear localization signal in the retinitis pigmentosa-mutated RP26 protein, ceramide kinase-like protein.

Retinitis pigmentosa (RP) is a genetically heterogeneous disease characterized by degeneration of the retina. A mutation in a new ceramide kinase (CERK) homologous gene, named CERK-like protein (CERKL), was found to cause autosomal recessive retinitis pigmentosa (RP26). Here, we show a point mutation of one of two putative nuclear localization signal (NLS) sequences inhibited the nuclear localization of the protein. Furthermore, the tetra-GFP-tagged NLS, which cannot passively enter the nucleus, was observed not only in the nucleus but also in the nucleolus. Our results provide the first evidence of the active nuclear import of CERKL and suggest that the identified NLS might be responsible for nucleolar retention of the protein. As recent studies have shown other RP-related proteins are localized in the nucleus or the nucleolus, our identification of NLS in CERKL suggests that CERKL likely plays important roles for retinal functions in the nucleus and the nucleolus.

Active Transport, Cell Nucleus↗