Together with the closely related MLP2, involved in the structural and functional organization of perinuclear chromatin (PubMed:10638763). Together with MLP2, associates with the nuclear pore complex and form filamentous structures along the nuclear periphery (PubMed:10085285, PubMed:24152732). Has a role in the localization of Esc1 to nucleolar regions (PubMed:24152732). Together with MLP2, mediates tethering of the some telomeres to the nuclear periphery, probably mediated by YKU70/YKU80 (HDF1/HDF2) heterodimer and show perinuclear location dependent silencing (PubMed:11862215). MLP1 and MLP2 are involved in telomere length regulation but not silencing or telomere anchoring (PubMed:12490156). Recognizes the 5'-splice site of pre-mRNAs and retains unspliced pre-mRNA in the nucleus without affecting splicing itself (PubMed:12490156, PubMed:12531921, PubMed:14718167). Component of the nuclear pore complex (NPC) (PubMed:24152732). NPC constitutes the exclusive means of nucleocytoplasmic transport (PubMed:24152732). NPCs allow the passive diffusion of ions and small molecules and the active, nuclear transport receptor-mediated bidirectional transport of macromolecules such as proteins, RNAs, ribonucleoparticles (RNPs), and ribosomal subunits across the nuclear envelope (PubMed:24152732). Due to its 8-fold rotational symmetry, all subunits are present with 8 copies or multiples thereof (PubMed:24152732). Interacts with NAB2, a hnRNP required for mRNA export (PubMed:12531921). Interacts with MLP2 (PubMed:16027220). Distributed fairly evenly along a C-shaped portion of the nuclear periphery, where the spindle pole body localizes in 90% of the cases. May be phosphorylated by CDC28. Present with 2710 molecules/cell in log phase SD medium. PubMed:8154186 misquoted the gene name as 'MPL1'.