Question: Is p100 the precursor protein molecule of the NF-kappaB transcription factor subunit p50?

Context:
We previously reported that alymphoplasia (aly/aly) mice, which have a natural loss-of-function mutation in the Nik gene, which encodes a kinase essential for the processing of p100 to p52 in the alternative nuclear factor-κB (NF-κB) pathway, show mild osteopetrosis with an increase in several parameters of bone formation: 
Proteolytic processing of the nuclear factor (NF)-kappaB2 precursor protein p100 generates the active NF-kappaB2 subunit p52, which in turn transcriptionally up-regulates p100 expression. 
The mammalian Rel/NF-kappaB family of transcription factors, including RelA, c-Rel, RelB, NF-kappaB1 (p50 and its precursor p105), and NF-kappaB2 (p52 and its precursor p100), plays a central role in the immune system by regulating several processes ranging from the development and survival of lymphocytes and lymphoid organs to the control of immune responses and malignant transformation.
NF-kappaB functions as a hetero- or homo-dimer which can be formed from five NF-kappaB subunits, NF-kappaB1 (p50 and its precursor p105), NF-kappaB2 (p52 and its precursor p100), RelA (p65), RelB and c-Rel.
The non-canonical pathway based on processing of NF-kappaB2 precursor protein p100 to generate p52 plays a critical role in controlling B cell function and lymphoid organogenesis.
Processing of NF-kappaB2 precursor protein p100 to generate p52 is tightly controlled, which is important for proper function of NF-kappaB.
Processing of NF-kappa B2 precursor protein p100 to generate p52 is tightly regulated. 
Processing of the NF-kappaB2 precursor protein p100 to generate p52 is an important step of NF-kappaB regulation.
Targeted disruption of the Rel/NF-kappaB family members NF-kappaB2, encoding p100/p52, and RelB in mice results in anatomical defects of secondary lymphoid tissues.
Here, we show that in T cells infected with the human T-cell leukemia virus (HTLV), IKKalpha is targeted to a novel signaling pathway that mediates processing of the nfkappab2 precursor protein p100, resulting in active production of the NF-kappaB subunit, p52.
nfkb2 encodes two members of the NF-kappa B/Rel family of proteins: p52 and p100. The p100 polypeptide has been proposed to serve as a precursor of p52, which corresponds to the N-terminal half of p100.
In most cells, small amounts of p52 are produced relative to the levels of p100, unlike the usually balanced production of nfkb1-derived p50 and p105. 
The alternative or second pathway proceeded via NF-kappaB-inducing kinase (NIK)-, IKKalpha-, and protein synthesis-dependent processing of the inhibitory NF-kappaB2 p100 precursor protein to the p52 form and resulted in a delayed but sustained activation of primarily RelB-containing NF-kappaB dimers.
In one exceptional case, generation of the p50 subunit of the transcriptional regulator NF-kappaB, the precursor protein p105 is processed in a limited manner: the N-terminal domain yields the p50 subunit, whereas the C-terminal domain is degraded
Proteolytic processing of the p105 precursor (NF-kappa B1) generates the p50 subunit of NF-kappa B
p105 (NFKB1) acts in a dual way as a cytoplasmic IkappaB molecule and as the source of the NF-kappaB p50 subunit upon processing
The p50 subunit of NF-kappa B is derived from the amino terminus of a 105 kilodalton precursor
Regulation of the transcription factor NF-kappaB involves proteasome-mediated processing of the NF-kappaB1 p105 precursor protein, which generates the p50 subunit of NF-kappaB
This effort identified NF-kappaB1 (p105), an atypical IkappaB molecule and the precursor of NF-kappaB subunit p50
NF-kappaB functions as a hetero- or homo-dimer which can be formed from five NF-kappaB subunits, NF-kappaB1 (p50 and its precursor p105), NF-kappaB2 (p52 and its precursor p100), RelA (p65), RelB and c-Rel
The mammalian Rel/NF-kappaB family of transcription factors, including RelA, c-Rel, RelB, NF-kappaB1 (p50 and its precursor p105), and NF-kappaB2 (p52 and its precursor p100), plays a central role in the immune system by regulating several processes ranging from the development and survival of lymphocytes and lymphoid organs to the control of immune responses and malignant transformation

Answer: No, the precursor molecule for NF-kappaB p50 is p105 and not p100. Nfkb2 encodes two members of the NF-kappa B/Rel family of proteins: p52 and p100. The p100 polypeptide has been proposed to serve as a precursor of p52 (and not of p50), which corresponds to the N-terminal half of p100. NF-kappaB functions as a hetero- or homo-dimer which can be formed from five NF-kappaB subunits, NF-kappaB1 (p50 and its precursor p105), NF-kappaB2 (p52 and its precursor p100), RelA (p65), RelB and c-Rel.
Exact answer: no